diff --git a/.gitignore b/.gitignore
index 4efa43ee..1740ad6d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,4 +4,7 @@ node_modules/
 *.log
 docs/
 coverage/
-dist
\ No newline at end of file
+dist
+yarn.lock
+package-lock.json
+pnpm-lock.yaml
\ No newline at end of file
diff --git a/src/database.ts b/src/database.ts
index c5cf7a5d..2a301479 100644
--- a/src/database.ts
+++ b/src/database.ts
@@ -7,6 +7,7 @@ import Schema from './schema';
 import SchemaType from './schematype';
 import WarehouseError from './error';
 import { logger } from 'hexo-log';
+import type { AddSchemaTypeOptions, NodeJSLikeCallback } from './types';
 
 const log = logger();
 const pkg = require('../package.json');
@@ -23,7 +24,7 @@ if (typeof writev === 'function') {
   };
 }
 
-async function exportAsync(database: Database, path: string) {
+async function exportAsync(database: Database, path: string): Promise<void> {
   const handle = await open(path, 'w');
 
   try {
@@ -79,7 +80,7 @@ interface DatabaseOptions {
 
 class Database {
   options: DatabaseOptions;
-  _models: any;
+  _models: Record<string, Model<any>>;
   Model: typeof Model;
 
   /**
@@ -103,7 +104,7 @@ class Database {
 
     this._models = {};
 
-    class _Model extends Model {}
+    class _Model extends Model<any> {}
 
     this.Model = _Model;
 
@@ -117,7 +118,7 @@ class Database {
    * @param {Schema|object} [schema]
    * @return {Model}
    */
-  model(name: string, schema?: any) {
+  model(name: string, schema?: Schema | Record<string, AddSchemaTypeOptions>): Model<any> {
     if (this._models[name]) {
       return this._models[name];
     }
@@ -133,7 +134,7 @@ class Database {
    * @param {function} [callback]
    * @return {Promise}
    */
-  load(callback?) {
+  load(callback?: NodeJSLikeCallback<any>): Bluebird<any> {
     const { path, onUpgrade, onDowngrade, version: newVersion } = this.options;
 
     if (!path) throw new WarehouseError('options.path is required');
@@ -173,14 +174,14 @@ class Database {
    * @param {function} [callback]
    * @return {Promise}
    */
-  save(callback?) {
+  save(callback?: NodeJSLikeCallback<any>): Bluebird<void> {
     const { path } = this.options;
 
     if (!path) throw new WarehouseError('options.path is required');
     return Bluebird.resolve(exportAsync(this, path)).asCallback(callback);
   }
 
-  toJSON() {
+  toJSON(): { meta: { version: number, warehouse: string }, models: Record<string, Model<any>> } {
     const models = Object.keys(this._models)
       .reduce((obj, key) => {
         const value = this._models[key];
diff --git a/src/document.ts b/src/document.ts
index 2c23b2e5..fcb5bbb3 100644
--- a/src/document.ts
+++ b/src/document.ts
@@ -1,17 +1,21 @@
 import rfdc from 'rfdc';
+import type Model from './model';
+import type Schema from './schema';
+import type { NodeJSLikeCallback } from './types';
 const cloneDeep = rfdc();
 
-abstract class Document {
-  abstract _model;
-  _id!: any;
-  abstract _schema;
+abstract class Document<T> {
+  abstract _model: Model<T>;
+  _id!: string | number | undefined;
+  abstract _schema: Schema;
+  [key : string]: any;
 
   /**
    * Document constructor.
    *
    * @param {object} data
    */
-  constructor(data) {
+  constructor(data?: T) {
     if (data) {
       Object.assign(this, data);
     }
@@ -23,7 +27,7 @@ abstract class Document {
    * @param {function} [callback]
    * @return {Promise}
    */
-  save(callback) {
+  save(callback?: NodeJSLikeCallback<any>): Promise<any> {
     return this._model.save(this, callback);
   }
 
@@ -34,7 +38,7 @@ abstract class Document {
    * @param {function} [callback]
    * @return {Promise}
    */
-  update(data, callback) {
+  update(data: object, callback?: NodeJSLikeCallback<any>): Promise<any> {
     return this._model.updateById(this._id, data, callback);
   }
 
@@ -45,7 +49,7 @@ abstract class Document {
    * @param {function} [callback]
    * @return {Promise}
    */
-  replace(data, callback) {
+  replace(data: T | Document<T>, callback?: NodeJSLikeCallback<any>): Promise<any> {
     return this._model.replaceById(this._id, data, callback);
   }
 
@@ -55,7 +59,7 @@ abstract class Document {
    * @param {function} [callback]
    * @return {Promise}
    */
-  remove(callback) {
+  remove(callback?: NodeJSLikeCallback<any>): Promise<any> {
     return this._model.removeById(this._id, callback);
   }
 
@@ -64,9 +68,9 @@ abstract class Document {
    *
    * @return {object}
    */
-  toObject() {
+  toObject(): T {
     const keys = Object.keys(this);
-    const obj = {};
+    const obj: Partial<T> = {};
 
     for (let i = 0, len = keys.length; i < len; i++) {
       const key = keys[i];
@@ -75,7 +79,7 @@ abstract class Document {
       obj[key] = isGetter(this, key) ? this[key] : cloneDeep(this[key]);
     }
 
-    return obj;
+    return obj as T;
   }
 
   /**
@@ -83,7 +87,7 @@ abstract class Document {
    *
    * @return {String}
    */
-  toString() {
+  toString(): string {
     return JSON.stringify(this);
   }
 
@@ -93,13 +97,13 @@ abstract class Document {
    * @param {String|Object} expr
    * @return {Document}
    */
-  populate(expr) {
+  populate(expr: string | any[] | { path?: string; model?: any; [key: PropertyKey]: any }): Document<T> {
     const stack = this._schema._parsePopulate(expr);
     return this._model._populate(this, stack);
   }
 }
 
-function isGetter(obj, key) {
+function isGetter(obj: any, key: PropertyKey): any {
   return Object.getOwnPropertyDescriptor(obj, key).get;
 }
 
diff --git a/src/lib/jsonstream/index.ts b/src/lib/jsonstream/index.ts
index e028660b..9a5dbf2f 100644
--- a/src/lib/jsonstream/index.ts
+++ b/src/lib/jsonstream/index.ts
@@ -7,7 +7,7 @@ import Parser from 'jsonparse';
  * @param {*} y
  * @returns {boolean}
  */
-const check = (x, y) => {
+const check = (x, y): boolean => {
   if (typeof x === 'string') {
     return y === x;
   }
@@ -27,7 +27,7 @@ const check = (x, y) => {
   return false;
 };
 
-export function parse(path, map = null) {
+export function parse(path: string | any[], map = null) {
   let header, footer;
 
   const parser = new Parser();
diff --git a/src/model.ts b/src/model.ts
index ea3e4ffa..32a6429d 100644
--- a/src/model.ts
+++ b/src/model.ts
@@ -10,26 +10,28 @@ import * as Types from './types/index';
 import WarehouseError from './error';
 import PopulationError from './error/population';
 import Mutex from './mutex';
+import type Database from './database';
+import type { AddSchemaTypeOptions, NodeJSLikeCallback, Options, PopulateResult } from './types';
 
-class Model extends EventEmitter {
+class Model<T> extends EventEmitter {
   _mutex = new Mutex();
-  data: Record<any, any> = {};
-  schema;
+  data: Record<PropertyKey, T> = {};
+  schema: Schema;
   length = 0;
   Document;
   Query;
-  _database;
+  _database: Database;
 
   /**
    * Model constructor.
    *
    * @param {string} name Model name
-   * @param {Schema|object} [schema] Schema
+   * @param {Schema|object} [schema_] Schema
    */
-  constructor(public name: string, schema_) {
+  constructor(public name: string, schema_: Schema | Record<string, AddSchemaTypeOptions>) {
     super();
 
-    let schema;
+    let schema: Schema;
 
     // Define schema
     if (schema_ instanceof Schema) {
@@ -47,10 +49,10 @@ class Model extends EventEmitter {
 
     this.schema = schema;
 
-    class _Document extends Document {
-      _model!: Model;
+    class _Document<T> extends Document<T> {
+      _model!: Model<T>;
       _schema!: Schema;
-      constructor(data) {
+      constructor(data: T) {
         super(data);
 
         // Apply getters
@@ -63,8 +65,8 @@ class Model extends EventEmitter {
     _Document.prototype._model = this;
     _Document.prototype._schema = schema;
 
-    class _Query extends Query {
-      _model!: Model;
+    class _Query<T> extends Query<T> {
+      _model!: Model<T>;
       _schema!: Schema;
     }
 
@@ -86,7 +88,7 @@ class Model extends EventEmitter {
    * @param {object} data
    * @return {Document}
    */
-  new(data) {
+  new(data?: T): Document<T> {
     return new this.Document(data);
   }
 
@@ -98,7 +100,7 @@ class Model extends EventEmitter {
    *   @param {boolean} [options.lean=false] Returns a plain JavaScript object
    * @return {Document|object}
    */
-  findById(id, options_?) {
+  findById(id: PropertyKey, options_?: Options): Document<T> | T {
     const raw = this.data[id];
     if (!raw) return;
 
@@ -116,7 +118,7 @@ class Model extends EventEmitter {
    * @param {*} id
    * @return {boolean}
    */
-  has(id) {
+  has(id: PropertyKey): boolean {
     return Boolean(this.data[id]);
   }
 
@@ -143,11 +145,11 @@ class Model extends EventEmitter {
    * @return {Promise}
    * @private
    */
-  _insertOne(data_) {
+  _insertOne(data_: Document<T> | T): Promise<any> {
     const schema = this.schema;
 
     // Apply getters
-    const data = data_ instanceof this.Document ? data_ : this.new(data_);
+    const data = (data_ instanceof this.Document ? data_ : this.new(data_ as T)) as Document<T>;
     const id = data._id;
 
     // Check ID
@@ -161,7 +163,7 @@ class Model extends EventEmitter {
 
     // Apply setters
     const result = data.toObject();
-    schema._applySetters(result);
+    schema._applySetters(result as object);
 
     // Pre-hooks
     return execHooks(schema, 'pre', 'save', data).then(data => {
@@ -181,7 +183,7 @@ class Model extends EventEmitter {
    * @param {function} [callback]
    * @return {Promise}
    */
-  insertOne(data, callback?) {
+  insertOne(data: Document<T> | T, callback?: NodeJSLikeCallback<any>): Promise<any> {
     return Promise.using(this._acquireWriteLock(), () => this._insertOne(data)).asCallback(callback);
   }
 
@@ -192,9 +194,9 @@ class Model extends EventEmitter {
    * @param {function} [callback]
    * @return {Promise}
    */
-  insert(data, callback) {
+  insert(data: Document<T> | T | Document<T>[] | T[], callback?: NodeJSLikeCallback<any>): Promise<any> {
     if (Array.isArray(data)) {
-      return Promise.mapSeries(data, item => this.insertOne(item)).asCallback(callback);
+      return Promise.mapSeries<Document<T> | T, any>(data, item => this.insertOne(item)).asCallback(callback);
     }
 
     return this.insertOne(data, callback);
@@ -207,8 +209,8 @@ class Model extends EventEmitter {
    * @param {function} [callback]
    * @return {Promise}
    */
-  save(data, callback) {
-    const id = data._id;
+  save(data: Document<T> | T, callback?: NodeJSLikeCallback<any>): Promise<any> {
+    const id = (data as any)._id;
 
     if (!id) return this.insertOne(data, callback);
 
@@ -229,7 +231,7 @@ class Model extends EventEmitter {
    * @return {Promise}
    * @private
    */
-  _updateWithStack(id, stack): Promise<any> {
+  _updateWithStack(id: string | number, stack: ((data: any) => void)[]): Promise<any> {
     const schema = this.schema;
 
     const data = this.data[id];
@@ -251,7 +253,7 @@ class Model extends EventEmitter {
 
     // Apply setters
     result = doc.toObject();
-    schema._applySetters(result);
+    schema._applySetters(result as object);
 
     // Pre-hooks
     return execHooks(schema, 'pre', 'save', doc).then(data => {
@@ -271,9 +273,9 @@ class Model extends EventEmitter {
    * @param {function} [callback]
    * @return {Promise}
    */
-  updateById(id, update, callback?) {
+  updateById(id: string | number, update: object, callback?: NodeJSLikeCallback<any>): Promise<any> {
     return Promise.using(this._acquireWriteLock(), () => {
-      const stack = this.schema._parseUpdate(update);
+      const stack = this.schema._parseUpdate(update as object);
       return this._updateWithStack(id, stack);
     }).asCallback(callback);
   }
@@ -286,8 +288,8 @@ class Model extends EventEmitter {
    * @param {function} [callback]
    * @return {Promise}
    */
-  update(query, data, callback?) {
-    return this.find(query).update(data, callback);
+  update(query: object, data: object, callback?: NodeJSLikeCallback<any>): Promise<any> {
+    return (this.find(query) as Query<T>).update(data, callback);
   }
 
   /**
@@ -298,21 +300,21 @@ class Model extends EventEmitter {
    * @return {Promise}
    * @private
    */
-  _replaceById(id, data_) {
+  _replaceById(id: string | number, data_: Document<T> | T): Promise<any> {
     const schema = this.schema;
 
     if (!this.has(id)) {
       return Promise.reject(new WarehouseError('ID `' + id + '` does not exist', WarehouseError.ID_NOT_EXIST));
     }
 
-    data_._id = id;
+    (data_ as any)._id = id;
 
     // Apply getters
-    const data = data_ instanceof this.Document ? data_ : this.new(data_);
+    const data = (data_ instanceof this.Document ? data_ : this.new(data_ as T)) as Document<T>;
 
     // Apply setters
     const result = data.toObject();
-    schema._applySetters(result);
+    schema._applySetters(result as object);
 
     // Pre-hooks
     return execHooks(schema, 'pre', 'save', data).then(data => {
@@ -332,7 +334,7 @@ class Model extends EventEmitter {
    * @param {function} [callback]
    * @return {Promise}
    */
-  replaceById(id, data, callback?) {
+  replaceById(id: string | number, data: Document<T> | T, callback?: NodeJSLikeCallback<any>): Promise<any> {
     return Promise.using(this._acquireWriteLock(), () => this._replaceById(id, data)).asCallback(callback);
   }
 
@@ -344,19 +346,18 @@ class Model extends EventEmitter {
    * @param {function} [callback]
    * @return {Promise}
    */
-  replace(query, data, callback?) {
-    return this.find(query).replace(data, callback);
+  replace(query: object, data, callback?: NodeJSLikeCallback<any>): Promise<any> {
+    return (this.find(query) as Query<T>).replace(data, callback);
   }
 
   /**
    * Finds a document by its identifier and remove it.
    *
    * @param {*} id
-   * @param {function} [callback]
    * @return {Promise}
    * @private
    */
-  _removeById(id) {
+  _removeById(id: string | number): Promise<any> {
     const schema = this.schema;
 
     const data = this.data[id];
@@ -383,7 +384,7 @@ class Model extends EventEmitter {
    * @param {function} [callback]
    * @return {Promise}
    */
-  removeById(id, callback) {
+  removeById(id: string | number, callback?: NodeJSLikeCallback<any>): Promise<any> {
     return Promise.using(this._acquireWriteLock(), () => this._removeById(id)).asCallback(callback);
   }
 
@@ -391,17 +392,17 @@ class Model extends EventEmitter {
    * Removes matching documents.
    *
    * @param {object} query
-   * @param {object} [callback]
+   * @param {function} [callback]
    * @return {Promise}
    */
-  remove(query, callback) {
-    return this.find(query).remove(callback);
+  remove(query: object, callback?: NodeJSLikeCallback<any>): Promise<any> {
+    return (this.find(query) as Query<T>).remove(callback);
   }
 
   /**
    * Deletes a model.
    */
-  destroy() {
+  destroy(): void {
     this._database._models[this.name] = null;
   }
 
@@ -410,7 +411,7 @@ class Model extends EventEmitter {
    *
    * @return {number}
    */
-  count() {
+  count(): number {
     return this.length;
   }
 
@@ -420,7 +421,7 @@ class Model extends EventEmitter {
    * @param {function} iterator
    * @param {object} [options] See {@link Model#findById}.
    */
-  forEach(iterator, options?) {
+  forEach(iterator: (value: any, index: number) => void, options?: Options): void {
     const keys = Object.keys(this.data);
     let num = 0;
 
@@ -436,7 +437,7 @@ class Model extends EventEmitter {
    * @param {Object} [options] See {@link Model#findById}.
    * @return {Array}
    */
-  toArray(options?) {
+  toArray(options?: Options): any[] {
     const result = new Array(this.length);
 
     this.forEach((item, i) => {
@@ -456,14 +457,16 @@ class Model extends EventEmitter {
    *   @param {Boolean} [options.lean=false] Returns a plain JavaScript object.
    * @return {Query|Array}
    */
-  find(query, options: { limit?: number; skip?: number; lean?: boolean; } = {}) {
+  find(query: object): Query<T>;
+  find(query: object, options: Options): Query<T> | T[];
+  find(query: object, options: Options = {}): Query<T> | T[] {
     const filter = this.schema._execQuery(query);
     const keys = Object.keys(this.data);
     const len = keys.length;
     let limit = options.limit || this.length;
     let skip = options.skip;
     const data = this.data;
-    const arr = [];
+    const arr: (T | Document<T>)[] = [];
 
     for (let i = 0; limit && i < len; i++) {
       const key = keys[i];
@@ -491,11 +494,13 @@ class Model extends EventEmitter {
    *   @param {Boolean} [options.lean=false] Returns a plain JavaScript object.
    * @return {Document|Object}
    */
-  findOne(query, options_ : { skip?: number; lean?: boolean; } = {}) {
+  findOne(query: object): Document<T>;
+  findOne(query: object, options_ : Options): Document<T> | T;
+  findOne(query: object, options_ : Options = {}): Document<T> | T {
     const options = Object.assign(options_, { limit: 1 });
 
     const result = this.find(query, options);
-    return options.lean ? result[0] : result.data[0];
+    return options.lean ? (result as any[])[0] : (result as Query<T>).toArray()[0];
   }
 
   /**
@@ -505,7 +510,7 @@ class Model extends EventEmitter {
    * @param {String|Number} [order]
    * @return {Query}
    */
-  sort(orderby, order) {
+  sort(orderby: string | object, order?: string | number): Query<T> {
     const sort = parseArgs(orderby, order);
     const fn = this.schema._execSort(sort);
 
@@ -520,7 +525,7 @@ class Model extends EventEmitter {
    * @param {Object} [options] See {@link Model#findById}.
    * @return {Document|Object}
    */
-  eq(i_, options?) {
+  eq(i_: number, options?: Options): Document<T> | Record<PropertyKey, any> {
     let index = i_ < 0 ? this.length + i_ : i_;
     const data = this.data;
     const keys = Object.keys(data);
@@ -545,7 +550,7 @@ class Model extends EventEmitter {
    * @param {Object} [options] See {@link Model#findById}.
    * @return {Document|Object}
    */
-  first(options) {
+  first(options?: Options): Document<T> | Record<PropertyKey, any> {
     return this.eq(0, options);
   }
 
@@ -555,7 +560,7 @@ class Model extends EventEmitter {
    * @param {Object} [options] See {@link Model#findById}.
    * @return {Document|Object}
    */
-  last(options) {
+  last(options?: Options): Document<T> | Record<PropertyKey, any> {
     return this.eq(-1, options);
   }
 
@@ -566,7 +571,7 @@ class Model extends EventEmitter {
    * @param {Number} [end]
    * @return {Query}
    */
-  slice(start_: number, end_?: number) {
+  slice(start_?: number, end_?: number): Query<T> {
     const total = this.length;
 
     let start = start_ | 0;
@@ -605,7 +610,7 @@ class Model extends EventEmitter {
    * @param {Number} i
    * @return {Query}
    */
-  limit(i) {
+  limit(i: number): Query<T> {
     return this.slice(0, i);
   }
 
@@ -615,7 +620,7 @@ class Model extends EventEmitter {
    * @param {Number} i
    * @return {Query}
    */
-  skip(i) {
+  skip(i: number): Query<T> {
     return this.slice(i);
   }
 
@@ -624,7 +629,7 @@ class Model extends EventEmitter {
    *
    * @return {Query}
    */
-  reverse() {
+  reverse(): Query<T> {
     return new this.Query(this.toArray().reverse());
   }
 
@@ -633,7 +638,7 @@ class Model extends EventEmitter {
    *
    * @return {Query}
    */
-  shuffle() {
+  shuffle(): Query<T> {
     return new this.Query(shuffle(this.toArray()));
   }
 
@@ -644,7 +649,7 @@ class Model extends EventEmitter {
    * @param {Object} [options]
    * @return {Array}
    */
-  map(iterator, options) {
+  map<T>(iterator: (value: any, index: number) => T, options?: Options): T[] {
     const result = new Array(this.length);
     const keys = Object.keys(this.data);
     const len = keys.length;
@@ -668,10 +673,10 @@ class Model extends EventEmitter {
    * @param {*} [initial] By default, the initial value is the first document.
    * @return {*}
    */
-  reduce(iterator, initial) {
+  reduce<T>(iterator: (pre: any, cur: any, index: number) => T, initial?: T): T {
     const arr = this.toArray();
     const len = this.length;
-    let i, result;
+    let i: number, result: any;
 
     if (initial === undefined) {
       i = 1;
@@ -696,7 +701,7 @@ class Model extends EventEmitter {
    * @param {*} [initial] By default, the initial value is the last document.
    * @return {*}
    */
-  reduceRight(iterator, initial) {
+  reduceRight<T>(iterator: (pre: any, cur: any, index: number) => T, initial?: T): T {
     const arr = this.toArray();
     const len = this.length;
     let i, result;
@@ -724,10 +729,10 @@ class Model extends EventEmitter {
    * @param {Object} [options]
    * @return {Query}
    */
-  filter(iterator, options) {
+  filter(iterator: (value: any, index: number) => any, options?: Options): Query<T> {
     const arr = [];
 
-    this.forEach((item, i) => {
+    this.forEach((item: any, i: number) => {
       if (iterator(item, i)) arr.push(item);
     }, options);
 
@@ -741,7 +746,7 @@ class Model extends EventEmitter {
    * @param {Function} iterator
    * @return {Boolean}
    */
-  every(iterator) {
+  every(iterator: (value: any, index: number) => any): boolean {
     const keys = Object.keys(this.data);
     const len = keys.length;
     let num = 0;
@@ -766,7 +771,7 @@ class Model extends EventEmitter {
    * @param {Function} iterator
    * @return {Boolean}
    */
-  some(iterator) {
+  some(iterator: (value: any, index: number) => any): boolean {
     const keys = Object.keys(this.data);
     const len = keys.length;
     let num = 0;
@@ -793,9 +798,9 @@ class Model extends EventEmitter {
    * @return {Function}
    * @private
    */
-  _populateGetter(data, model, options) {
+  _populateGetter(data: string | number, model: Model<T>, options: unknown) {
     let hasCache = false;
-    let cache;
+    let cache: Record<PropertyKey, any> | Document<T>;
 
     return () => {
       if (!hasCache) {
@@ -816,10 +821,10 @@ class Model extends EventEmitter {
    * @return {Function}
    * @private
    */
-  _populateGetterArray(data, model, options) {
+  _populateGetterArray(data: any[], model: Model<T>, options: Options): () => any[] | Query<T> {
     const Query = model.Query;
     let hasCache = false;
-    let cache;
+    let cache: any[] | Query<T>;
 
     return () => {
       if (!hasCache) {
@@ -830,7 +835,7 @@ class Model extends EventEmitter {
         }
 
         if (options.match) {
-          cache = new Query(arr).find(options.match, options);
+          cache = (new Query(arr) as Query<T>).find(options.match, options);
         } else if (options.skip) {
           if (options.limit) {
             arr = arr.slice(options.skip, options.skip + options.limit);
@@ -864,7 +869,7 @@ class Model extends EventEmitter {
    * @return {Object}
    * @private
    */
-  _populate(data, stack) {
+  _populate(data: Document<T>, stack: PopulateResult[]): Document<T> {
     const models = this._database._models;
 
     for (let i = 0, len = stack.length; i < len; i++) {
@@ -894,7 +899,7 @@ class Model extends EventEmitter {
    * @param {String|Object} path
    * @return {Query}
    */
-  populate(path) {
+  populate(path: string | any[] | { path?: string; model?: any; [key: PropertyKey]: any }): Query<T> {
     if (!path) throw new TypeError('path is required');
 
     const stack = this.schema._parsePopulate(path);
@@ -913,14 +918,14 @@ class Model extends EventEmitter {
    * @param {Array} arr
    * @private
    */
-  _import(arr) {
+  _import(arr: any[]) {
     const len = arr.length;
     const data = this.data;
     const schema = this.schema;
 
     for (let i = 0; i < len; i++) {
       const item = arr[i];
-      data[item._id] = schema._parseDatabase(item);
+      data[item._id] = schema._parseDatabase(item) as T;
     }
 
     this.length = len;
@@ -932,11 +937,11 @@ class Model extends EventEmitter {
    * @return {String}
    * @private
    */
-  _export() {
+  _export(): string {
     return JSON.stringify(this.toJSON());
   }
 
-  toJSON() {
+  toJSON(): any[] {
     const result = new Array(this.length);
     const { data, schema } = this;
     const keys = Object.keys(data);
@@ -945,20 +950,20 @@ class Model extends EventEmitter {
     for (let i = 0, num = 0; i < length; i++) {
       const raw = data[keys[i]];
       if (raw) {
-        result[num++] = schema._exportDatabase(cloneDeep(raw));
+        result[num++] = schema._exportDatabase(cloneDeep(raw) as object);
       }
     }
     return result;
   }
-  get: Model['findById'];
-  size: Model['count'];
-  each: Model['forEach'];
-  random: Model['shuffle'];
+  get: Model<T>['findById'];
+  size: Model<T>['count'];
+  each: Model<T>['forEach'];
+  random: Model<T>['shuffle'];
 }
 
 Model.prototype.get = Model.prototype.findById;
 
-function execHooks(schema, type, event, data) {
+function execHooks(schema: Schema, type: string, event: string, data: any): Promise<any> {
   const hooks = schema.hooks[type][event] as ((data: any) => Promise<void> | void)[];
   if (!hooks.length) return Promise.resolve(data);
 
diff --git a/src/mutex.ts b/src/mutex.ts
index 6eaa0ab4..dec0dbea 100644
--- a/src/mutex.ts
+++ b/src/mutex.ts
@@ -6,7 +6,7 @@ class Mutex {
     this._queue = [];
   }
 
-  lock(fn: () => void) {
+  lock(fn: () => void): void {
     if (this._locked) {
       this._queue.push(fn);
       return;
@@ -16,7 +16,7 @@ class Mutex {
     fn();
   }
 
-  unlock() {
+  unlock(): void {
     if (!this._locked) return;
 
     const next = this._queue.shift();
diff --git a/src/query.ts b/src/query.ts
index 0eb8fae4..d9445909 100644
--- a/src/query.ts
+++ b/src/query.ts
@@ -1,17 +1,23 @@
 import Promise from 'bluebird';
 import { parseArgs, shuffle } from './util';
+import type Model from './model';
+import type Schema from './schema';
+import type Document from './document';
+import type { NodeJSLikeCallback, Options } from './types';
 
-abstract class Query {
+abstract class Query<T> {
+  data: Document<T>[];
   length: number;
-  abstract _model;
-  abstract _schema;
+  abstract _model: Model<T>;
+  abstract _schema: Schema;
 
   /**
    * Query constructor.
    *
    * @param {Array} data
    */
-  constructor(private data: any[]) {
+  constructor(data: Document<T>[]) {
+    this.data = data;
     this.length = data.length;
   }
 
@@ -42,7 +48,7 @@ abstract class Query {
    *
    * @return {Array}
    */
-  toArray(): any[] {
+  toArray(): Document<T>[] {
     return this.data;
   }
 
@@ -53,7 +59,7 @@ abstract class Query {
    * @param {Number} i
    * @return {Document|Object}
    */
-  eq(i: number) {
+  eq(i: number): Document<T> {
     const index = i < 0 ? this.length + i : i;
     return this.data[index];
   }
@@ -63,7 +69,7 @@ abstract class Query {
    *
    * @return {Document|Object}
    */
-  first() {
+  first(): Document<T> {
     return this.eq(0);
   }
 
@@ -72,7 +78,7 @@ abstract class Query {
    *
    * @return {Document|Object}
    */
-  last() {
+  last(): Document<T> {
     return this.eq(-1);
   }
 
@@ -83,7 +89,7 @@ abstract class Query {
    * @param {Number} [end]
    * @return {Query}
    */
-  slice(start: number, end?: number): Query {
+  slice(start: number, end?: number): Query<T> {
     return Reflect.construct(this.constructor, [this.data.slice(start, end)]);
   }
 
@@ -93,7 +99,7 @@ abstract class Query {
    * @param {Number} i
    * @return {Query}
    */
-  limit(i: number): Query {
+  limit(i: number): Query<T> {
     return this.slice(0, i);
   }
 
@@ -103,7 +109,7 @@ abstract class Query {
    * @param {Number} i
    * @return {Query}
    */
-  skip(i: number): Query {
+  skip(i: number): Query<T> {
     return this.slice(i);
   }
 
@@ -112,7 +118,7 @@ abstract class Query {
    *
    * @return {Query}
    */
-  reverse(): Query {
+  reverse(): Query<T> {
     return Reflect.construct(this.constructor, [this.data.slice().reverse()]);
   }
 
@@ -121,7 +127,7 @@ abstract class Query {
    *
    * @return {Query}
    */
-  shuffle(): Query {
+  shuffle(): Query<T> {
     return Reflect.construct(this.constructor, [shuffle(this.data)]);
   }
 
@@ -135,7 +141,9 @@ abstract class Query {
    *   @param {Boolean} [options.lean=false] Returns a plain JavaScript object.
    * @return {Query|Array}
    */
-  find(query: any, options: { limit?: number; skip?: number; lean?: boolean; } = {}): any[] | Query {
+  find(query: object): Query<T>;
+  find(query: object, options: Options): T[] | Query<T>;
+  find(query: object, options: Options = {}): T[] | Query<T> {
     const filter = this._schema._execQuery(query);
     const { data, length } = this;
     const { lean = false } = options;
@@ -167,7 +175,9 @@ abstract class Query {
    *   @param {Boolean} [options.lean=false] Returns a plain JavaScript object.
    * @return {Document|Object}
    */
-  findOne(query: any, options: { skip?: number; lean?: boolean; } = {}): any {
+  findOne(query: object): Document<T>;
+  findOne(query: object, options): Document<T> | T;
+  findOne(query: object, options: Options = {}): Document<T> | T {
     const _options = Object.assign(options, { limit: 1 });
 
     const result = this.find(query, _options);
@@ -192,7 +202,7 @@ abstract class Query {
    * @param {String|Number} [order]
    * @return {Query}
    */
-  sort(orderby, order): Query {
+  sort(orderby: string | object, order?: string | number | object): Query<T> {
     const sort = parseArgs(orderby, order);
     const fn = this._schema._execSort(sort);
 
@@ -224,9 +234,9 @@ abstract class Query {
    * @param {*} [initial] By default, the initial value is the first document.
    * @return {*}
    */
-  reduce(iterator, initial?) {
+  reduce<R>(iterator: (pre: any, cur: any, index: number) => R, initial?: R): R {
     const { data, length } = this;
-    let result, i;
+    let result, i: number;
 
     if (initial === undefined) {
       i = 1;
@@ -251,7 +261,7 @@ abstract class Query {
    * @param {*} [initial] By default, the initial value is the last document.
    * @return {*}
    */
-  reduceRight(iterator, initial?) {
+  reduceRight<R>(iterator: (pre: any, cur: any, index: number) => R, initial?: R): R {
     const { data, length } = this;
     let result, i;
 
@@ -277,7 +287,7 @@ abstract class Query {
    * @param {Function} iterator
    * @return {Query}
    */
-  filter(iterator: (item: any, index: number) => boolean): Query {
+  filter(iterator: (item: any, index: number) => boolean): Query<T> {
     const { data, length } = this;
     const arr = [];
 
@@ -330,7 +340,7 @@ abstract class Query {
    * @param {Function} [callback]
    * @return {Promise}
    */
-  update(data: any, callback?: (err?: any) => void): Promise<any> {
+  update(data: any, callback?: NodeJSLikeCallback<any>): Promise<any> {
     const model = this._model;
     const stack = this._schema._parseUpdate(data);
 
@@ -344,7 +354,7 @@ abstract class Query {
    * @param {Function} [callback]
    * @return {Promise}
    */
-  replace(data: any, callback?: (err?: any) => void): Promise<any> {
+  replace(data: any, callback?: NodeJSLikeCallback<any>): Promise<any> {
     const model = this._model;
 
     return Promise.map(this.data, item => model.replaceById(item._id, data)).asCallback(callback);
@@ -356,7 +366,7 @@ abstract class Query {
    * @param {Function} [callback]
    * @return {Promise}
    */
-  remove(callback) {
+  remove(callback?: NodeJSLikeCallback<any>): Promise<any> {
     const model = this._model;
 
     return Promise.mapSeries(this.data, item => model.removeById(item._id)).asCallback(callback);
@@ -368,7 +378,7 @@ abstract class Query {
    * @param {String|Object} expr
    * @return {Query}
    */
-  populate(expr: any): Query {
+  populate(expr: string | any[] | { path?: string; model?: any; [key: PropertyKey]: any }): Query<T> {
     const stack = this._schema._parsePopulate(expr);
     const { data, length } = this;
     const model = this._model;
@@ -380,9 +390,9 @@ abstract class Query {
     return this;
   }
 
-  size: Query['count'];
-  each: Query['forEach'];
-  random: Query['shuffle'];
+  size: Query<T>['count'];
+  each: Query<T>['forEach'];
+  random: Query<T>['shuffle'];
 }
 
 Query.prototype.size = Query.prototype.count;
diff --git a/src/schema.ts b/src/schema.ts
index f9f81590..933a3598 100644
--- a/src/schema.ts
+++ b/src/schema.ts
@@ -5,18 +5,21 @@ import { getProp, setProp, delProp } from './util';
 import PopulationError from './error/population';
 import SchemaTypeVirtual from './types/virtual';
 import { isPlainObject } from 'is-plain-object';
+import type { AddSchemaTypeLoopOptions, AddSchemaTypeOptions, PopulateResult, SchemaTypeOptions } from './types';
 
 /**
  * @callback queryFilterCallback
  * @param {*} data
  * @return {boolean}
  */
+type queryFilterCallback = (data: unknown) => boolean;
 
 /**
  * @callback queryCallback
  * @param {*} data
  * @return {void}
  */
+type queryCallback = (data: unknown) => void;
 
 /**
  * @callback queryParseCallback
@@ -24,18 +27,13 @@ import { isPlainObject } from 'is-plain-object';
  * @param {*} b
  * @returns {*}
  */
-
-/**
- * @typedef PopulateResult
- * @property {string} path
- * @property {*} model
- */
+type queryParseCallback = (a: unknown, b: unknown) => number;
 
 const builtinTypes = new Set(['String', 'Number', 'Boolean', 'Array', 'Object', 'Date', 'Buffer']);
 
-const getSchemaType = (name, options) => {
-  const Type = options.type || options;
-  const typeName = Type.name;
+const getSchemaType = (name: string, options: { type: SchemaTypeOptions; [key: string]: any } | SchemaTypeOptions) => {
+  const Type = (options as any).type || options;
+  const typeName: string = Type.name;
 
   if (builtinTypes.has(typeName)) {
     return new Types[typeName](name, options);
@@ -44,13 +42,13 @@ const getSchemaType = (name, options) => {
   return new Type(name, options);
 };
 
-const checkHookType = type => {
+const checkHookType = (type: string) => {
   if (type !== 'save' && type !== 'remove') {
     throw new TypeError('Hook type must be `save` or `remove`!');
   }
 };
 
-const hookWrapper = fn => {
+const hookWrapper = (fn: (...args: any[]) => void): (...args: any[]) => Promise<any> => {
   if (fn.length > 1) {
     return Promise.promisify(fn);
   }
@@ -61,11 +59,11 @@ const hookWrapper = fn => {
 /**
  * @param {Function[]} stack
  */
-const execSortStack = stack => {
+const execSortStack = (stack: ((a: unknown, b: unknown) => number)[]) => {
   const len = stack.length;
 
-  return (a, b) => {
-    let result;
+  return (a: any, b: any) => {
+    let result: number;
 
     for (let i = 0; i < len; i++) {
       result = stack[i](a, b);
@@ -76,32 +74,32 @@ const execSortStack = stack => {
   };
 };
 
-const sortStack = (path_, key, sort) => {
+const sortStack = (path_: SchemaType<any>, key: string, sort: string | number) => {
   const path = path_ || new SchemaType(key);
   const descending = sort === 'desc' || sort === -1;
 
-  return (a, b) => {
+  return (a: any, b: any) => {
     const result = path.compare(getProp(a, key), getProp(b, key));
     return descending && result ? result * -1 : result;
   };
 };
 
 class UpdateParser {
-  static updateStackNormal(key, update) {
-    return data => { setProp(data, key, update); };
+  static updateStackNormal(key: string, update: any) {
+    return (data: any) => { setProp(data, key, update); };
   }
 
-  static updateStackOperator(path_, ukey, key, update) {
+  static updateStackOperator(path_: SchemaType<unknown>, ukey: string | number, key: string, update: any) {
     const path = path_ || new SchemaType(key);
 
-    return data => {
+    return (data: any) => {
       const result = path[ukey](getProp(data, key), update, data);
       setProp(data, key, result);
     };
   }
 
   // eslint-disable-next-line no-useless-constructor
-  constructor(private paths) {}
+  constructor(private paths: Record<string, SchemaType<any>>) { }
 
   /**
    * Parses updating expressions and returns a stack.
@@ -110,11 +108,11 @@ class UpdateParser {
    * @param {queryCallback[]} [stack]
    * @private
    */
-  parseUpdate(updates, prefix = '', stack = []) {
+  parseUpdate(updates: object, prefix = '', stack: queryCallback[] = []): queryCallback[] {
     const { paths } = this;
     const { updateStackOperator } = UpdateParser;
     const keys = Object.keys(updates);
-    let path, prefixNoDot;
+    let path: SchemaType<any>, prefixNoDot: string;
 
     if (prefix) {
       prefixNoDot = prefix.substring(0, prefix.length - 1);
@@ -158,7 +156,7 @@ class UpdateParser {
  */
 class QueryParser {
   // eslint-disable-next-line no-useless-constructor
-  constructor(private paths) {}
+  constructor(private paths: Record<string, SchemaType<any>>) { }
 
   /**
    *
@@ -166,10 +164,10 @@ class QueryParser {
    * @param {*} query
    * @return {queryFilterCallback}
    */
-  queryStackNormal(name, query) {
+  queryStackNormal(name: string, query: unknown): queryFilterCallback {
     const path = this.paths[name] || new SchemaType(name);
 
-    return data => path.match(getProp(data, name), query, data);
+    return (data: unknown) => path.match(getProp(data, name), query, data);
   }
 
   /**
@@ -179,7 +177,7 @@ class QueryParser {
    * @param {*} query
    * @return {queryFilterCallback}
    */
-  queryStackOperator(qkey, name, query) {
+  queryStackOperator(qkey: string, name: string, query: any): queryFilterCallback {
     const path = this.paths[name] || new SchemaType(name);
 
     return data => path[qkey](getProp(data, name), query, data);
@@ -191,7 +189,7 @@ class QueryParser {
    * @return {void}
    * @private
    */
-  $and(arr, stack) {
+  $and(arr: any[], stack: queryFilterCallback[]): void {
     for (let i = 0, len = arr.length; i < len; i++) {
       stack.push(this.execQuery(arr[i]));
     }
@@ -202,7 +200,7 @@ class QueryParser {
    * @return {queryFilterCallback}
    * @private
    */
-  $or(query) {
+  $or(query: any[]): queryFilterCallback {
     const stack = this.parseQueryArray(query);
     const len = stack.length;
 
@@ -220,7 +218,7 @@ class QueryParser {
    * @return {queryFilterCallback}
    * @private
    */
-  $nor(query) {
+  $nor(query: any[]): queryFilterCallback {
     const stack = this.parseQueryArray(query);
     const len = stack.length;
 
@@ -238,7 +236,7 @@ class QueryParser {
    * @return {queryFilterCallback}
    * @private
    */
-  $not(query) {
+  $not(query: any): queryFilterCallback {
     const stack = this.parseQuery(query);
     const len = stack.length;
 
@@ -262,7 +260,7 @@ class QueryParser {
    * @return {queryFilterCallback}
    * @private
    */
-  $where(fn) {
+  $where(fn: (...args: any[]) => boolean): queryFilterCallback {
     return data => Reflect.apply(fn, data, []);
   }
 
@@ -273,7 +271,7 @@ class QueryParser {
    * @return {queryFilterCallback[]}
    * @private
    */
-  parseQueryArray(arr) {
+  parseQueryArray(arr: any[]): queryFilterCallback[] {
     const stack = [];
     this.$and(arr, stack);
     return stack;
@@ -288,7 +286,7 @@ class QueryParser {
    * @return {void}
    * @private
    */
-  parseNormalQuery(queries, prefix, stack = []) {
+  parseNormalQuery(queries: object, prefix: string, stack: queryFilterCallback[] = []): void {
     const keys = Object.keys(queries);
 
     for (let i = 0, len = keys.length; i < len; i++) {
@@ -316,10 +314,10 @@ class QueryParser {
    * @return {queryFilterCallback[]}
    * @private
    */
-  parseQuery(queries) {
+  parseQuery(queries: any): queryFilterCallback[] {
 
     /** @type {queryFilterCallback[]} */
-    const stack = [];
+    const stack: queryFilterCallback[] = [];
     const keys = Object.keys(queries);
 
     for (let i = 0, len = keys.length; i < len; i++) {
@@ -366,7 +364,7 @@ class QueryParser {
    * @return {queryFilterCallback}
    * @private
    */
-  execQuery(query) {
+  execQuery(query: object): queryFilterCallback {
     const stack = this.parseQuery(query);
     const len = stack.length;
 
@@ -380,19 +378,34 @@ class QueryParser {
   }
 }
 
+
 class Schema {
   paths: Record<string, SchemaType<any>> = {};
-  statics: Record<string, any> = {};
-  methods: Record<string, any> = {};
-  hooks;
-  stacks;
+  statics: Record<string, (...args: any[]) => any> = {};
+  methods: Record<string, (...args: any[]) => any> = {};
+  hooks: {
+    pre: {
+      save: ((...args: any[]) => Promise<any>)[]
+      remove: ((...args: any[]) => Promise<any>)[]
+    };
+    post: {
+      save: ((...args: any[]) => Promise<any>)[]
+      remove: ((...args: any[]) => Promise<any>)[]
+    };
+  };
+  stacks: {
+    getter: ((data: object) => void)[];
+    setter: ((data: object) => void)[];
+    import: ((data: object) => void)[];
+    export: ((data: object) => void)[];
+  };
 
   /**
    * Schema constructor.
    *
    * @param {Object} [schema]
    */
-  constructor(schema?) {
+  constructor(schema?: Record<string, AddSchemaTypeOptions>) {
     this.hooks = {
       pre: {
         save: [],
@@ -422,7 +435,7 @@ class Schema {
    * @param {Object} schema
    * @param {String} prefix
    */
-  add(schema: Record<string, any>, prefix = ''): void {
+  add(schema: Record<string, AddSchemaTypeOptions>, prefix = ''): void {
     const keys = Object.keys(schema);
     const len = keys.length;
 
@@ -444,8 +457,8 @@ class Schema {
    * @return {SchemaType | undefined}
    */
   path(name: string): SchemaType<any>;
-  path(name: string, obj: SchemaType<unknown> | ((...args: any[]) => any) | { type: any; } | Record<string, unknown> | any[]): void;
-  path(name: string, obj?: SchemaType<unknown> | ((...args: any[]) => any) | { type: any; } | Record<string, unknown> | any[]): SchemaType<any> | void {
+  path(name: string, obj: AddSchemaTypeOptions): void;
+  path(name: string, obj?: AddSchemaTypeOptions): SchemaType<any> | void {
     if (obj == null) {
       return this.paths[name];
     }
@@ -458,7 +471,7 @@ class Schema {
     } else {
       switch (typeof obj) {
         case 'function':
-          type = getSchemaType(name, {type: obj});
+          type = getSchemaType(name, { type: obj });
           break;
 
         case 'object':
@@ -467,7 +480,7 @@ class Schema {
               child: obj.length ? getSchemaType(name, obj[0]) : new SchemaType(name)
             });
           } else if (obj.type) {
-            type = getSchemaType(name, obj);
+            type = getSchemaType(name, obj as { type: SchemaTypeOptions; });
           } else {
             type = new Types.Object();
             nested = Object.keys(obj).length > 0;
@@ -483,7 +496,7 @@ class Schema {
     this.paths[name] = type;
     this._updateStack(name, type);
 
-    if (nested) this.add(obj, `${name}.`);
+    if (nested) this.add(obj as AddSchemaTypeLoopOptions, `${name}.`);
   }
 
   /**
@@ -493,7 +506,7 @@ class Schema {
    * @param {SchemaType} type
    * @private
    */
-  _updateStack(name: string, type: SchemaType<unknown>) {
+  _updateStack(name: string, type: SchemaType<unknown>): void {
     const { stacks } = this;
 
     stacks.getter.push(data => {
@@ -559,7 +572,7 @@ class Schema {
    * @param {String} type Hook type. One of `save` or `remove`.
    * @param {Function} fn
    */
-  pre(type, fn) {
+  pre(type: 'save' | 'remove', fn: (...args: any[]) => void): void {
     checkHookType(type);
     if (typeof fn !== 'function') throw new TypeError('Hook must be a function!');
 
@@ -572,7 +585,7 @@ class Schema {
    * @param {String} type Hook type. One of `save` or `remove`.
    * @param {Function} fn
    */
-  post(type, fn) {
+  post(type: 'save' | 'remove', fn: (...args: any[]) => void): void {
     checkHookType(type);
     if (typeof fn !== 'function') throw new TypeError('Hook must be a function!');
 
@@ -585,7 +598,7 @@ class Schema {
    * @param {String} name
    * @param {Function} fn
    */
-  method(name, fn) {
+  method(name: string, fn: (...args: any[]) => any) {
     if (!name) throw new TypeError('Method name is required!');
 
     if (typeof fn !== 'function') {
@@ -601,7 +614,7 @@ class Schema {
    * @param {String} name
    * @param {Function} fn
    */
-  static(name: string, fn) {
+  static(name: string, fn: (...args: any[]) => any) {
     if (!name) throw new TypeError('Method name is required!');
 
     if (typeof fn !== 'function') {
@@ -618,7 +631,7 @@ class Schema {
    * @return {void}
    * @private
    */
-  _applyGetters(data) {
+  _applyGetters(data: object): void {
     const stack = this.stacks.getter;
 
     for (let i = 0, len = stack.length; i < len; i++) {
@@ -633,7 +646,7 @@ class Schema {
    * @return {void}
    * @private
    */
-  _applySetters(data) {
+  _applySetters(data: object): void {
     const stack = this.stacks.setter;
 
     for (let i = 0, len = stack.length; i < len; i++) {
@@ -648,7 +661,7 @@ class Schema {
    * @return {Object}
    * @private
    */
-  _parseDatabase(data) {
+  _parseDatabase(data: object): object {
     const stack = this.stacks.import;
 
     for (let i = 0, len = stack.length; i < len; i++) {
@@ -665,7 +678,7 @@ class Schema {
    * @return {Object}
    * @private
    */
-  _exportDatabase(data) {
+  _exportDatabase(data: object): object {
     const stack = this.stacks.export;
 
     for (let i = 0, len = stack.length; i < len; i++) {
@@ -682,7 +695,7 @@ class Schema {
    * @return {queryCallback[]}
    * @private
    */
-  _parseUpdate(updates) {
+  _parseUpdate(updates: object): queryCallback[] {
     return new UpdateParser(this.paths).parseUpdate(updates);
   }
 
@@ -693,7 +706,7 @@ class Schema {
    * @return {queryFilterCallback}
    * @private
    */
-  _execQuery(query) {
+  _execQuery(query: object): queryFilterCallback {
     return new QueryParser(this.paths).execQuery(query);
   }
 
@@ -707,7 +720,7 @@ class Schema {
    * @return {queryParseCallback[]}
    * @private
    */
-  _parseSort(sorts, prefix = '', stack = []) {
+  _parseSort(sorts: object, prefix = '', stack: queryParseCallback[] = []): queryParseCallback[] {
     const { paths } = this;
     const keys = Object.keys(sorts);
 
@@ -733,7 +746,7 @@ class Schema {
    * @return {queryParseCallback}
    * @private
    */
-  _execSort(sorts) {
+  _execSort(sorts: object): queryParseCallback {
     const stack = this._parseSort(sorts);
     return execSortStack(stack);
   }
@@ -746,7 +759,7 @@ class Schema {
    * @private
    */
   // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types
-  _parsePopulate(expr) {
+  _parsePopulate(expr: string | any[] | { path?: string; model?: any; [key: PropertyKey]: any }): PopulateResult[] {
     const { paths } = this;
     const arr = [];
 
diff --git a/src/schematype.ts b/src/schematype.ts
index 22dea735..0ba0b6d2 100644
--- a/src/schematype.ts
+++ b/src/schematype.ts
@@ -56,7 +56,7 @@ class SchemaType<T> {
    *   @param {Boolean} [options.required=false]
    *   @param {*} [options.default]
    */
-  constructor(public name = '', options?: { required?: boolean; default?: (() => T) | T; }) {
+  constructor(public name: string = '', options?: { required?: boolean; default?: (() => T) | T; }) {
     this.options = Object.assign({
       required: false
     }, options);
@@ -64,7 +64,7 @@ class SchemaType<T> {
     const default_ = this.options.default;
 
     if (typeof default_ === 'function') {
-      this.default = default_ as unknown as () => T;
+      this.default = default_ as () => T;
     } else {
       this.default = () => default_;
     }
@@ -244,7 +244,7 @@ class SchemaType<T> {
    * @param {Object} data
    * @return {Boolean}
    */
-  q$nin(value, query, data?) {
+  q$nin(value: unknown, query: unknown[], data?: unknown): boolean {
     return !query.includes(value);
   }
 
@@ -256,7 +256,7 @@ class SchemaType<T> {
    * @param {Object} data
    * @return {*}
    */
-  u$set(value, update, data?) {
+  u$set<T>(value: unknown, update: T, data?: unknown): T {
     return update;
   }
 
@@ -268,7 +268,7 @@ class SchemaType<T> {
    * @param {Object} data
    * @return {*}
    */
-  u$unset(value, update, data?) { return update ? undefined : value; }
+  u$unset<T>(value: T, update: boolean, data?: unknown): T | undefined { return update ? undefined : value; }
 
   /**
    * Renames a field.
@@ -278,7 +278,7 @@ class SchemaType<T> {
    * @param {Object} data
    * @return {*}
    */
-  u$rename(value, update, data): void {
+  u$rename(value: unknown, update: unknown, data: unknown): void {
     if (value !== undefined) setProp(data, update, value);
     return undefined;
   }
diff --git a/src/types.ts b/src/types.ts
new file mode 100644
index 00000000..21f6107f
--- /dev/null
+++ b/src/types.ts
@@ -0,0 +1,32 @@
+import type SchemaType from './schematype';
+
+export type NodeJSLikeCallback<R, E = any> = (err: E, result?: R) => void
+
+export interface Options {
+  lean?: boolean;
+  skip?: number;
+  limit?: number;
+  [key: PropertyKey]: any;
+}
+
+export type SchemaTypeOptions = typeof SchemaType<unknown> | SchemaType<unknown> | ((...args: any[]) => any)
+
+export type AddSchemaTypeSimpleOptions = SchemaTypeOptions | { type: SchemaTypeOptions; [key: string]: any };
+
+export type AddSchemaTypeMixedOptions = AddSchemaTypeSimpleOptions | AddSchemaTypeSimpleOptions[];
+
+export interface AddSchemaTypeLoopOptions {
+  [key: string]: AddSchemaTypeMixedOptions | AddSchemaTypeLoopOptions;
+}
+
+export type AddSchemaTypeOptions = AddSchemaTypeMixedOptions | AddSchemaTypeLoopOptions;
+
+/**
+ * @typedef PopulateResult
+ * @property {string} path
+ * @property {*} model
+ */
+export type PopulateResult = {
+  path: string;
+  model: any;
+};
diff --git a/src/types/array.ts b/src/types/array.ts
index 3c51f36f..dd27c7f9 100644
--- a/src/types/array.ts
+++ b/src/types/array.ts
@@ -29,13 +29,15 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
   /**
    * Casts an array and its child elements.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {Array}
    */
-  cast(value_?: unknown, data?: unknown): I[] | null | undefined {
+  cast(value_: Exclude<unknown, null | undefined>, data?: unknown): I[];
+  cast(value_?: unknown, data?: unknown): I[] | undefined;
+  cast(value_?: unknown, data?: unknown): I[] | undefined {
     value_ = super.cast(value_, data);
-    if (value_ == null) return value_ as null | undefined;
+    if (value_ == null) return value_ as undefined;
 
     const value = isArray(value_) ? value_ : value_ = [value_];
     if (!value.length) return value;
@@ -52,7 +54,7 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
   /**
    * Validates an array and its child elements.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {Array|Error}
    */
@@ -107,8 +109,10 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
    * @param {Array} value
    * @return {Array}
    */
-  parse(value?: unknown[]) {
-    if (!value) return value;
+  parse(value: unknown[]): I[];
+  parse(): undefined;
+  parse(value?: unknown[]): I[] | undefined {
+    if (!value) return value as undefined;
 
     const len = value.length;
     if (!len) return [];
@@ -117,7 +121,7 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
     const child = this.child;
 
     for (let i = 0; i < len; i++) {
-      result[i] = child.parse(value[i]);
+      result[i] = child.parse(value[i]) as I;
     }
 
     return result;
@@ -130,8 +134,10 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
    * @param {Object} data
    * @return {Array}
    */
-  value(value?: unknown[], data?: unknown): any[] {
-    if (!value) return value;
+  value(value: unknown[], data?: unknown): any[]
+  value(): undefined;
+  value(value?: unknown[], data?: unknown): any[] | undefined {
+    if (!value) return value as undefined;
 
     const len = value.length;
     if (!len) return [];
@@ -211,7 +217,7 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
    * @param {Object} data
    * @return {Boolean}
    */
-  q$nin(value?: unknown[], query?: unknown[], data?: unknown): boolean {
+  q$nin<T>(value?: T[], query?: T[], data?: unknown): boolean {
     if (!value) return true;
 
     for (let i = 0, len = query.length; i < len; i++) {
@@ -229,7 +235,7 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
    * @param {Object} data
    * @return {Boolean}
    */
-  q$all(value?: unknown[], query?: unknown[], data?: unknown): boolean {
+  q$all<T>(value?: T[], query?: T[], data?: unknown): boolean {
     if (!value) return false;
 
     for (let i = 0, len = query.length; i < len; i++) {
@@ -268,7 +274,7 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
    * @param {Object} data
    * @return {Array}
    */
-  u$unshift(value?: unknown[], update?: unknown, data?: unknown): any[] {
+  u$unshift<T>(value?: T[], update?: T | T[], data?: unknown): T[] {
     if (isArray(update)) {
       return value ? update.concat(value) : update;
     }
@@ -289,7 +295,7 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
    * @param {Object} data
    * @return {Array}
    */
-  u$pull(value?: unknown[], update?: unknown, data?: unknown): any[] {
+  u$pull<T>(value?: T[], update?: T | T[], data?: unknown): T[] {
     if (!value) return value;
 
     if (isArray(update)) {
@@ -307,7 +313,7 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
    * @param {Object} data
    * @return {Array}
    */
-  u$shift(value?, update?, data?) {
+  u$shift<T>(value?: T[], update?: number | boolean, data?: unknown): T[] {
     if (!value || !update) return value;
 
     if (update === true) {
@@ -327,7 +333,7 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
    * @param {Object} data
    * @return {Array}
    */
-  u$pop(value?, update?, data?) {
+  u$pop<T>(value?: T[], update?: number | boolean, data?: unknown): T[] {
     if (!value || !update) return value;
 
     const length = value.length;
@@ -349,7 +355,7 @@ class SchemaTypeArray<I, T extends SchemaType<I>> extends SchemaType<I[]> {
    * @param {Object} data
    * @return {Array}
    */
-  u$addToSet(value?: any[], update?, data?) {
+  u$addToSet<T>(value?: T[], update?: T | T[], data?: unknown): T[] {
     if (isArray(update)) {
       if (!value) return update;
 
diff --git a/src/types/boolean.ts b/src/types/boolean.ts
index 55330fde..1160dfe2 100644
--- a/src/types/boolean.ts
+++ b/src/types/boolean.ts
@@ -9,7 +9,7 @@ class SchemaTypeBoolean extends SchemaType<boolean> {
   /**
    * Casts a boolean.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {Boolean}
    */
@@ -24,7 +24,7 @@ class SchemaTypeBoolean extends SchemaType<boolean> {
   /**
    * Validates a boolean.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {Boolean|Error}
    */
diff --git a/src/types/buffer.ts b/src/types/buffer.ts
index 73cc157e..f5927ff1 100644
--- a/src/types/buffer.ts
+++ b/src/types/buffer.ts
@@ -14,7 +14,7 @@ class SchemaTypeBuffer extends SchemaType<Buffer> {
    *   @param {boolean|Function} [options.default]
    *   @param {string} [options.encoding=hex]
    */
-  constructor(name: string, options?) {
+  constructor(name: string, options?: Partial<SchemaType<Buffer>['options']> & { encoding?: BufferEncoding; }) {
     super(name, Object.assign({
       encoding: 'hex'
     }, options));
@@ -23,14 +23,16 @@ class SchemaTypeBuffer extends SchemaType<Buffer> {
   /**
    * Casts data.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {Buffer}
    */
-  cast(value_?: unknown, data?): Buffer | null | undefined {
+  cast(value_: WithImplicitCoercion<Uint8Array | ReadonlyArray<number> | string>, data?: unknown): Buffer;
+  cast(value_?: unknown, data?: unknown): Buffer | undefined;
+  cast(value_?: unknown, data?: unknown): Buffer | undefined {
     const value = super.cast(value_, data);
 
-    if (value == null || Buffer.isBuffer(value)) return value as Buffer | null | undefined;
+    if (value == null || Buffer.isBuffer(value)) return value as Buffer | undefined;
     if (typeof value === 'string') return Buffer.from(value, this.options.encoding);
     if (Array.isArray(value)) return Buffer.from(value);
   }
@@ -38,11 +40,11 @@ class SchemaTypeBuffer extends SchemaType<Buffer> {
   /**
    * Validates data.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {Buffer}
    */
-  validate(value_: unknown, data?): Buffer {
+  validate(value_: unknown, data?: unknown): Buffer {
     const value = super.validate(value_, data);
 
     if (!Buffer.isBuffer(value)) {
@@ -73,7 +75,9 @@ class SchemaTypeBuffer extends SchemaType<Buffer> {
    * @param {*} value
    * @return {Boolean}
    */
-  parse(value?) {
+  parse(value: WithImplicitCoercion<Uint8Array | ReadonlyArray<number> | string>): Buffer;
+  parse(value?: unknown): Buffer | null | undefined;
+  parse(value?: any): Buffer | null | undefined {
     return value ? Buffer.from(value, this.options.encoding) : value;
   }
 
@@ -81,9 +85,9 @@ class SchemaTypeBuffer extends SchemaType<Buffer> {
    * Transforms data into number to compress the size of database files.
    *
    * @param {Buffer} value
-   * @return {Number}
+   * @return {String}
    */
-  value(value?: Buffer) {
+  value(value?: Buffer): string {
     return Buffer.isBuffer(value) ? value.toString(this.options.encoding) : value;
   }
 
diff --git a/src/types/cuid.ts b/src/types/cuid.ts
index 49b057c6..476cfa0c 100644
--- a/src/types/cuid.ts
+++ b/src/types/cuid.ts
@@ -14,7 +14,7 @@ class SchemaTypeCUID extends SchemaType<string> {
    * @param {String} value
    * @return {String}
    */
-  cast(value?) {
+  cast(value?: string): string {
     if (value == null && this.options.required) {
       return cuid();
     }
@@ -28,7 +28,7 @@ class SchemaTypeCUID extends SchemaType<string> {
    * @param {*} value
    * @return {String|Error}
    */
-  validate(value?) {
+  validate(value?: string): string {
     if (value && (value[0] !== 'c' || value.length !== 25)) {
       throw new ValidationError(`\`${value}\` is not a valid CUID`);
     }
diff --git a/src/types/date.ts b/src/types/date.ts
index 40727b87..398d09e6 100644
--- a/src/types/date.ts
+++ b/src/types/date.ts
@@ -9,17 +9,15 @@ class SchemaTypeDate extends SchemaType<Date> {
   /**
    * Casts data.
    *
-   * @param {*} value
+   * @param {*} value_
    * @return {Date | null | undefined}
    */
-  cast(value_?): Date | null | undefined;
-  cast(value_: Date): Date;
-  cast(value_: null): Date | null;
-  cast(value_: undefined): Date | undefined;
-  cast(value_: unknown): Date | null | undefined {
+  cast(value_: Date | number | string): Date;
+  cast(value_?: unknown): Date | undefined;
+  cast(value_?: unknown): Date | undefined {
     const value = super.cast(value_, null);
 
-    if (value == null || value instanceof Date) return value as Date | null | undefined;
+    if (value == null || value instanceof Date) return value as Date | undefined;
 
     return new Date(value as any);
   }
@@ -27,18 +25,18 @@ class SchemaTypeDate extends SchemaType<Date> {
   /**
    * Validates data.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {Date|Error}
    */
-  validate(value_, data?) {
+  validate(value_: unknown, data?: unknown): Date {
     const value = super.validate(value_, data);
 
     if (value != null && (!(value instanceof Date) || isNaN(value.getTime()))) {
       throw new ValidationError(`\`${value}\` is not a valid date!`);
     }
 
-    return value;
+    return value as Date;
   }
 
   /**
@@ -63,9 +61,9 @@ class SchemaTypeDate extends SchemaType<Date> {
    * @param {Date} b
    * @return {Number}
    */
-  compare(a?, b?) {
+  compare(a?: Date, b?: Date): number {
     if (a) {
-      return b ? a - b : 1;
+      return b ? a.getTime() - b.getTime() : 1;
     }
 
     return b ? -1 : 0;
@@ -77,7 +75,9 @@ class SchemaTypeDate extends SchemaType<Date> {
    * @param {*} value
    * @return {Date}
    */
-  parse(value?) {
+  parse(value: string | number | Date): Date;
+  parse(): undefined;
+  parse(value?: string | number | Date): Date | undefined {
     if (value) return new Date(value);
   }
 
@@ -87,8 +87,10 @@ class SchemaTypeDate extends SchemaType<Date> {
    * @param {Date} value
    * @return {String}
    */
-  value(value?) {
-    return value ? value.toISOString() : value;
+  value(value: Date): string;
+  value(): undefined;
+  value(value?: Date): string | undefined {
+    return value ? value.toISOString() : value as undefined;
   }
 
   /**
@@ -98,7 +100,7 @@ class SchemaTypeDate extends SchemaType<Date> {
    * @param {Number} query
    * @return {Boolean}
    */
-  q$day(value, query) {
+  q$day(value: Date | undefined, query: number): boolean {
     return value ? value.getDate() === query : false;
   }
 
@@ -109,7 +111,7 @@ class SchemaTypeDate extends SchemaType<Date> {
    * @param {Number} query
    * @return {Boolean}
    */
-  q$month(value, query) {
+  q$month(value: Date | undefined, query: number): boolean {
     return value ? value.getMonth() === query : false;
   }
 
@@ -120,7 +122,7 @@ class SchemaTypeDate extends SchemaType<Date> {
    * @param {Number} query
    * @return {Boolean}
    */
-  q$year(value, query) {
+  q$year(value: Date | undefined, query: number): boolean {
     return value ? value.getFullYear() === query : false;
   }
 
@@ -131,7 +133,7 @@ class SchemaTypeDate extends SchemaType<Date> {
    * @param {Number} update
    * @return {Date}
    */
-  u$inc(value, update) {
+  u$inc(value: Date | undefined, update: number): Date {
     if (value) return new Date(value.getTime() + update);
   }
 
@@ -142,7 +144,7 @@ class SchemaTypeDate extends SchemaType<Date> {
    * @param {Number} update
    * @return {Date}
    */
-  u$dec(value, update) {
+  u$dec(value: Date | undefined, update: number): Date {
     if (value) return new Date(value.getTime() - update);
   }
 }
diff --git a/src/types/enum.ts b/src/types/enum.ts
index 1a96d88c..42ee6c26 100644
--- a/src/types/enum.ts
+++ b/src/types/enum.ts
@@ -15,7 +15,7 @@ class SchemaTypeEnum extends SchemaType<any[]> {
    *   @param {Array} options.elements
    *   @param {*} [options.default]
    */
-  constructor(name, options) {
+  constructor(name: string, options?: Partial<SchemaType<any[]>['options']> & { elements?: any[] }) {
     super(name, Object.assign({
       elements: []
     }, options));
@@ -24,11 +24,11 @@ class SchemaTypeEnum extends SchemaType<any[]> {
   /**
    * Validates data. The value must be one of elements set in the options.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {*}
    */
-  validate(value_, data?) {
+  validate(value_: unknown, data?: unknown) {
     const value = super.validate(value_, data);
     const elements = this.options.elements;
 
diff --git a/src/types/integer.ts b/src/types/integer.ts
index 97b74d5e..c5400212 100644
--- a/src/types/integer.ts
+++ b/src/types/integer.ts
@@ -9,11 +9,11 @@ class SchemaTypeInteger extends SchemaTypeNumber {
   /**
    * Casts a integer.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {Number}
    */
-  cast(value_?, data?): number {
+  cast(value_?: unknown, data?: unknown): number {
     const value = super.cast(value_, data);
 
     return parseInt(value as any, 10);
@@ -22,11 +22,11 @@ class SchemaTypeInteger extends SchemaTypeNumber {
   /**
    * Validates an integer.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {Number|Error}
    */
-  validate(value_?, data?): number {
+  validate(value_?: unknown, data?: unknown): number {
     const value = super.validate(value_, data);
 
     if (!Number.isInteger(value)) {
diff --git a/src/types/number.ts b/src/types/number.ts
index 83dcbe2c..6b0a072d 100644
--- a/src/types/number.ts
+++ b/src/types/number.ts
@@ -13,10 +13,12 @@ class SchemaTypeNumber extends SchemaType<number> {
    * @param {Object} data
    * @return {Number}
    */
-  cast(value_?, data?): number | null | undefined {
+  cast(value_: Exclude<unknown, undefined | null>, data?: unknown): number;
+  cast(value_?: unknown, data?: unknown): number | undefined;
+  cast(value_?: unknown, data?: unknown): number | undefined {
     const value = super.cast(value_, data);
 
-    if (value == null || typeof value === 'number') return value as number | null | undefined;
+    if (value == null || typeof value === 'number') return value as number | undefined;
 
     return +value;
   }
@@ -28,14 +30,14 @@ class SchemaTypeNumber extends SchemaType<number> {
    * @param {Object} data
    * @return {Number|Error}
    */
-  validate(value_?, data?) {
+  validate(value_?: unknown, data?: unknown): number {
     const value = super.validate(value_, data);
 
     if (value !== undefined && (typeof value !== 'number' || isNaN(value))) {
       throw new ValidationError(`\`${value}\` is not a number!`);
     }
 
-    return value;
+    return value as number;
   }
 
   /**
@@ -45,7 +47,7 @@ class SchemaTypeNumber extends SchemaType<number> {
    * @param {Number} update
    * @return {Number}
    */
-  u$inc(value, update) {
+  u$inc(value: number | undefined, update: number): number {
     return value ? value + update : update;
   }
 
@@ -56,7 +58,7 @@ class SchemaTypeNumber extends SchemaType<number> {
    * @param {Number} update
    * @return {Number}
    */
-  u$dec(value, update) {
+  u$dec(value: number | undefined, update: number): number {
     return value ? value - update : -update;
   }
 
@@ -67,7 +69,7 @@ class SchemaTypeNumber extends SchemaType<number> {
    * @param {Number} update
    * @return {Number}
    */
-  u$mul(value, update) {
+  u$mul(value: number | undefined, update: number): number {
     return value ? value * update : 0;
   }
 
@@ -78,7 +80,7 @@ class SchemaTypeNumber extends SchemaType<number> {
    * @param {Number} update
    * @return {Number}
    */
-  u$div(value, update) {
+  u$div(value: number | undefined, update: number): number {
     return value ? value / update : 0;
   }
 
@@ -89,7 +91,7 @@ class SchemaTypeNumber extends SchemaType<number> {
    * @param {Number} update
    * @return {Number}
    */
-  u$mod(value, update) {
+  u$mod(value: number | undefined, update: number): number {
     return value ? value % update : 0;
   }
 
@@ -100,7 +102,7 @@ class SchemaTypeNumber extends SchemaType<number> {
    * @param {Number} update
    * @return {Number}
    */
-  u$max(value, update) {
+  u$max(value: number | undefined, update: number): number {
     return update > value ? update : value;
   }
 
@@ -111,7 +113,7 @@ class SchemaTypeNumber extends SchemaType<number> {
    * @param {Number} update
    * @return {Number}
    */
-  u$min(value, update) {
+  u$min(value: number | undefined, update: number): number {
     return update < value ? update : value;
   }
 }
diff --git a/src/types/object.ts b/src/types/object.ts
index 840fa20c..7024288d 100644
--- a/src/types/object.ts
+++ b/src/types/object.ts
@@ -12,7 +12,7 @@ class SchemaTypeObject extends SchemaType<Record<string, any>> {
    *   @param {Boolean} [options.required=false]
    *   @param {Object|Function} [options.default={}]
    */
-  constructor(name?, options?) {
+  constructor(name?: string, options?: Partial<SchemaType<Record<string, any>>['options']>) {
     super(name, Object.assign({ default: {} }, options));
   }
 }
diff --git a/src/types/string.ts b/src/types/string.ts
index 589ee085..03d9be1f 100644
--- a/src/types/string.ts
+++ b/src/types/string.ts
@@ -9,32 +9,34 @@ class SchemaTypeString extends SchemaType<string> {
   /**
    * Casts a string.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {String}
    */
-  cast(value_?, data?) {
+  cast(value_: { toString(): string }, data?: unknown): string;
+  cast(value_?: unknown, data?: unknown): string | undefined;
+  cast(value_?: unknown, data?: unknown): string | undefined {
     const value = super.cast(value_, data);
 
-    if (value == null || typeof value === 'string') return value;
+    if (value == null || typeof value === 'string') return value as string | undefined;
     if (typeof value.toString === 'function') return value.toString();
   }
 
   /**
    * Validates a string.
    *
-   * @param {*} value
+   * @param {*} value_
    * @param {Object} data
    * @return {String|Error}
    */
-  validate(value_?, data?) {
+  validate(value_?: unknown, data?: unknown): string {
     const value = super.validate(value_, data);
 
     if (value !== undefined && typeof value !== 'string') {
       throw new ValidationError(`\`${value}\` is not a string!`);
     }
 
-    return value;
+    return value as string;
   }
 
   /**
@@ -45,13 +47,13 @@ class SchemaTypeString extends SchemaType<string> {
    * @param {Object} data
    * @return {Boolean}
    */
-  match(value, query, data?) {
+  match(value: string | undefined, query: string | RegExp | undefined, data?: unknown): boolean {
     if (!value || !query) {
       return value === query;
     }
 
-    if (typeof query.test === 'function') {
-      return query.test(value);
+    if (typeof(query as any).test === 'function') {
+      return (query as RegExp).test(value);
     }
 
     return value === query;
@@ -65,7 +67,7 @@ class SchemaTypeString extends SchemaType<string> {
    * @param {Object} data
    * @return {Boolean}
    */
-  q$in(value, query, data?) {
+  q$in(value: string | undefined, query: string[] | RegExp[], data?: unknown): boolean {
     for (let i = 0, len = query.length; i < len; i++) {
       if (this.match(value, query[i], data)) return true;
     }
@@ -81,7 +83,7 @@ class SchemaTypeString extends SchemaType<string> {
    * @param {Object} data
    * @return {Boolean}
    */
-  q$nin(value, query, data?) {
+  q$nin(value: string | undefined, query: string[] | RegExp[], data?: unknown): boolean {
     return !this.q$in(value, query, data);
   }
 
@@ -92,7 +94,7 @@ class SchemaTypeString extends SchemaType<string> {
    * @param {Number} query
    * @return {Boolean}
    */
-  q$length(value, query) {
+  q$length(value: string | undefined, query: number): boolean {
     return (value ? value.length : 0) === query;
   }
 }
diff --git a/src/types/virtual.ts b/src/types/virtual.ts
index aa333a5a..383907b3 100644
--- a/src/types/virtual.ts
+++ b/src/types/virtual.ts
@@ -14,7 +14,7 @@ class SchemaTypeVirtual extends SchemaType<any> {
    * @param {Function} fn
    * @chainable
    */
-  get(fn) {
+  get(fn: () => any): SchemaTypeVirtual {
     if (typeof fn !== 'function') {
       throw new TypeError('Getter must be a function!');
     }
@@ -30,7 +30,7 @@ class SchemaTypeVirtual extends SchemaType<any> {
    * @param {Function} fn
    * @chainable
    */
-  set(fn) {
+  set(fn: (value: any) => void): SchemaTypeVirtual {
     if (typeof fn !== 'function') {
       throw new TypeError('Setter must be a function!');
     }
@@ -47,7 +47,7 @@ class SchemaTypeVirtual extends SchemaType<any> {
    * @param {Object} data
    * @return {*}
    */
-  cast(value, data) {
+  cast(value: unknown, data: any): void {
     if (typeof this.getter !== 'function') return;
 
     const getter = this.getter;
@@ -70,7 +70,7 @@ class SchemaTypeVirtual extends SchemaType<any> {
    * @param {*} value
    * @param {Object} data
    */
-  validate(value, data) {
+  validate(value: any, data: any): void {
     if (typeof this.setter === 'function') {
       this.setter.call(data, value);
     }
diff --git a/src/util.ts b/src/util.ts
index 62cef092..b7ab5d57 100644
--- a/src/util.ts
+++ b/src/util.ts
@@ -1,8 +1,8 @@
-function extractPropKey(key) {
+function extractPropKey(key: string): string[] {
   return key.split('.');
 }
 
-function _parseArgs(args) {
+function _parseArgs(args: string) {
   if (typeof args !== 'string') return args;
 
   const arr = args.split(' ');
@@ -173,12 +173,12 @@ export function reverse(arr) {
   return arr;
 }
 
-export function parseArgs(orderby, order?) {
+export function parseArgs(orderby: string | object, order?: string | number | object) {
   let result;
 
   if (order) {
     result = {};
-    result[orderby] = order;
+    result[orderby as string] = order;
   } else if (typeof orderby === 'string') {
     result = _parseArgs(orderby);
   } else {
diff --git a/test/scripts/document.ts b/test/scripts/document.ts
index abac13a4..565215ff 100644
--- a/test/scripts/document.ts
+++ b/test/scripts/document.ts
@@ -2,18 +2,30 @@ import chai from 'chai';
 const should = chai.should(); // eslint-disable-line
 import Database from '../../dist/database';
 import Document from '../../dist/document';
+import type Model from '../../dist/model';
+
+interface UserType {
+  name?: string;
+  age?: number;
+  comments?: string;
+}
+
+interface CommentType {
+  content?: string;
+  author?: string;
+}
 
 describe('Document', () => {
   const db = new Database();
   const Schema = Database.Schema;
 
-  const User = db.model('User', {
+  const User: Model<UserType> = db.model('User', {
     name: String,
     age: Number,
     comments: [{type: Schema.Types.CUID, ref: 'Comment'}]
   });
 
-  const Comment = db.model('Comment', {
+  const Comment: Model<CommentType> = db.model('Comment', {
     content: String,
     author: {type: Schema.Types.CUID, ref: 'User'}
   });
@@ -39,7 +51,7 @@ describe('Document', () => {
     const doc = User.new({});
 
     return doc.save().then(item => {
-      User.findById(doc._id).should.exist;
+      User.findById(doc._id as string | number).should.exist;
       return User.removeById(item._id);
     });
   });
@@ -115,5 +127,5 @@ describe('Document', () => {
 
     user.populate('comments').comments.toArray().should.eql(comments);
     return comments;
-  }).map(comment => Comment.removeById(comment._id)));
+  }).map<unknown, any>(comment => Comment.removeById(comment._id)));
 });
diff --git a/test/scripts/model.ts b/test/scripts/model.ts
index 88589338..c5b20116 100644
--- a/test/scripts/model.ts
+++ b/test/scripts/model.ts
@@ -9,6 +9,26 @@ import Promise from 'bluebird';
 import sinon from 'sinon';
 import cuid from 'cuid';
 import Database from '../../dist/database';
+import type Query from '../../dist/query';
+import type Document from '../../dist/document';
+import type Model from '../../dist/model';
+
+interface UserType {
+  name?: {
+    first: string;
+    last: string;
+  }
+  email?: string;
+  age?: number;
+  posts?: string[];
+}
+
+interface PostType {
+  title?: string;
+  content?: string;
+  user_id?: string;
+  created?: Date;
+}
 
 describe('Model', () => {
 
@@ -38,8 +58,8 @@ describe('Model', () => {
     created: Date
   });
 
-  const User = db.model('User', userSchema);
-  const Post = db.model('Post', postSchema);
+  const User: Model<UserType> = db.model('User', userSchema);
+  const Post: Model<PostType> = db.model('Post', postSchema);
 
   it('new()', () => {
     const user = User.new({
@@ -48,7 +68,7 @@ describe('Model', () => {
       age: 20
     });
 
-    user._id.should.exist;
+    user._id!.should.exist;
     user.name.first.should.eql('John');
     user.name.last.should.eql('Doe');
     user.name.full.should.eql('John Doe');
@@ -98,16 +118,17 @@ describe('Model', () => {
     const doc = User.new();
     delete doc._id;
 
-    return User.insert(doc).should.eventually.be.rejected;
+    return (User.insert(doc) as any).should.eventually.be.rejected;
   });
 
   it('insert() - already existed', () => {
     let user;
 
-    return User.insert({}).then(data => {
+    // @ts-ignore
+    return (User.insert({}).then(data => {
       user = data;
       return User.insert(data);
-    }).finally(() => User.removeById(user._id)).should.eventually.be.rejected;
+    }).finally(() => User.removeById(user._id)) as any).should.eventually.be.rejected;
   });
 
   it('insert() - hook', () => {
@@ -150,7 +171,7 @@ describe('Model', () => {
   ]).then(data => {
     data.length = 2;
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('insert() - sync problem', () => {
     const db = new Database();
@@ -301,7 +322,7 @@ describe('Model', () => {
     return data;
   }).then(data => User.removeById(data._id)));
 
-  it('updateById() - id not exist', () => User.updateById('foo', {}).should.eventually.be.rejected);
+  it('updateById() - id not exist', () => (User.updateById('foo', {}) as any).should.eventually.be.rejected);
 
   it('updateById() - hook', () => {
     const db = new Database();
@@ -341,7 +362,7 @@ describe('Model', () => {
     updated[0].email.should.eql('A');
     updated[1].email.should.eql('A');
     return data;
-  })).map(item => User.removeById(item._id)));
+  })).map<unknown, any>(item => User.removeById(item._id)));
 
   it('replaceById()', () => {
     function validate(data) {
@@ -371,7 +392,7 @@ describe('Model', () => {
     }).then(data => User.removeById(data._id));
   });
 
-  it('replaceById() - id not exist', () => User.replaceById('foo', {}).should.eventually.be.rejected);
+  it('replaceById() - id not exist', () => (User.replaceById('foo', {}) as any).should.eventually.be.rejected);
 
   it('replaceById() - pre-hook', () => {
     const db = new Database();
@@ -411,7 +432,7 @@ describe('Model', () => {
     updated[0].email.should.eql('A');
     updated[1].email.should.eql('A');
     return data;
-  })).map(item => User.removeById(item._id)));
+  })).map<unknown, any>(item => User.removeById(item._id)));
 
   it('removeById()', () => {
     const listener = sinon.spy(data => {
@@ -430,7 +451,7 @@ describe('Model', () => {
     });
   });
 
-  it('removeById() - id not exist', () => User.removeById('foo', {}).should.eventually.be.rejected);
+  it('removeById() - id not exist', () => (User.removeById('foo', () => {}) as any).should.eventually.be.rejected);
 
   it('removeById() - hook', () => {
     const db = new Database();
@@ -489,13 +510,13 @@ describe('Model', () => {
 
       count.should.eql(data.length);
       return data;
-    }).map(item => Post.removeById(item._id));
+    }).map<unknown, any>(item => Post.removeById(item._id));
   });
 
   it('toArray()', () => Post.insert(Array(10).fill({})).then(data => {
     Post.toArray().should.eql(data);
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('find()', () => User.insert([
     {age: 10},
@@ -504,10 +525,10 @@ describe('Model', () => {
     {age: 30},
     {age: 40}
   ]).then(data => {
-    const query = User.find({age: 20});
+    const query = User.find({age: 20}) as Query<UserType>;
     query.data.should.eql(data.slice(1, 3));
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - blank', () => User.insert([
     {age: 10},
@@ -516,10 +537,10 @@ describe('Model', () => {
     {age: 30},
     {age: 40}
   ]).then(data => {
-    const query = User.find({});
+    const query = User.find({}) as Query<UserType>;
     query.data.should.eql(data);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - operator', () => User.insert([
     {age: 10},
@@ -527,10 +548,10 @@ describe('Model', () => {
     {age: 30},
     {age: 40}
   ]).then(data => {
-    const query = User.find({age: {$gt: 20}});
+    const query = User.find({age: {$gt: 20}}) as Query<UserType>;
     query.data.should.eql(data.slice(2));
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - limit', () => User.insert([
     {age: 10},
@@ -538,10 +559,10 @@ describe('Model', () => {
     {age: 30},
     {age: 40}
   ]).then(data => {
-    const query = User.find({age: {$gte: 20}}, {limit: 2});
+    const query = User.find({age: {$gte: 20}}, {limit: 2}) as Query<UserType>;
     query.data.should.eql(data.slice(1, 3));
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - skip', () => User.insert([
     {age: 10},
@@ -549,15 +570,15 @@ describe('Model', () => {
     {age: 30},
     {age: 40}
   ]).then(data => {
-    let query = User.find({age: {$gte: 20}}, {skip: 1});
+    let query = User.find({age: {$gte: 20}}, {skip: 1}) as Query<UserType>;
     query.data.should.eql(data.slice(2));
 
     // with limit
-    query = User.find({age: {$gte: 20}}, {limit: 1, skip: 1});
+    query = User.find({age: {$gte: 20}}, {limit: 1, skip: 1}) as Query<UserType>;
     query.data.should.eql(data.slice(2, 3));
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - lean', () => User.insert([
     {age: 10},
@@ -568,7 +589,7 @@ describe('Model', () => {
     const query = User.find({age: {$gt: 20}}, {lean: true});
     query.should.be.a('array');
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - $and', () => User.insert([
     {name: {first: 'John', last: 'Doe'}, age: 20},
@@ -582,10 +603,10 @@ describe('Model', () => {
       ]
     });
 
-    query.toArray().should.eql([data[1]]);
+    (query as Query<UserType>).toArray().should.eql([data[1]]);
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - $or', () => User.insert([
     {name: {first: 'John', last: 'Doe'}, age: 20},
@@ -599,10 +620,10 @@ describe('Model', () => {
       ]
     });
 
-    query.toArray().should.eql(data.slice(1));
+    (query as Query<UserType>).toArray().should.eql(data.slice(1));
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - $nor', () => User.insert([
     {name: {first: 'John', last: 'Doe'}, age: 20},
@@ -616,10 +637,10 @@ describe('Model', () => {
       ]
     });
 
-    query.toArray().should.eql([data[0]]);
+    (query as Query<UserType>).toArray().should.eql([data[0]]);
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - $not', () => User.insert([
     {name: {first: 'John', last: 'Doe'}, age: 20},
@@ -630,10 +651,10 @@ describe('Model', () => {
       $not: {'name.last': 'Doe'}
     });
 
-    query.toArray().should.eql(data.slice(2));
+    (query as Query<UserType>).toArray().should.eql(data.slice(2));
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - $where', () => User.insert([
     {name: {first: 'John', last: 'Doe'}, age: 20},
@@ -646,10 +667,10 @@ describe('Model', () => {
       }
     });
 
-    query.toArray().should.eql(data.slice(0, 2));
+    (query as Query<UserType>).toArray().should.eql(data.slice(0, 2));
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('findOne()', () => User.insert([
     {age: 10},
@@ -659,7 +680,7 @@ describe('Model', () => {
   ]).then(data => {
     User.findOne({age: {$gt: 20}}).should.eql(data[2]);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('findOne() - lean', () => User.insert([
     {age: 10},
@@ -667,9 +688,9 @@ describe('Model', () => {
     {age: 30},
     {age: 40}
   ]).then(data => {
-    User.findOne({age: {$gt: 20}}, {lean: true})._id.should.eql(data[2]._id);
+    (User.findOne({age: {$gt: 20}}, {lean: true}) as Document<UserType>)._id!.should.eql(data[2]._id);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('sort()', () => User.insert([
     {age: 15},
@@ -681,7 +702,7 @@ describe('Model', () => {
     query.data[1].should.eql(data[0]);
     query.data[2].should.eql(data[1]);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('sort() - descending', () => User.insert([
     {age: 15},
@@ -693,7 +714,7 @@ describe('Model', () => {
     query.data[1].should.eql(data[0]);
     query.data[2].should.eql(data[2]);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('sort() - multi', () => User.insert([
     {age: 15, email: 'A'},
@@ -707,7 +728,7 @@ describe('Model', () => {
     query.data[2].should.eql(data[3]);
     query.data[3].should.eql(data[1]);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('eq()', () => Post.insert(Array(5).fill({})).then(data => {
     for (let i = 0, len = data.length; i < len; i++) {
@@ -715,7 +736,7 @@ describe('Model', () => {
     }
 
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('eq() - negative index', () => Post.insert(Array(5).fill({})).then(data => {
     for (let i = 1, len = data.length; i <= len; i++) {
@@ -723,7 +744,7 @@ describe('Model', () => {
     }
 
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('eq() - no data', () => {
     (typeof Post.eq(1)).should.eql('undefined');
@@ -733,68 +754,68 @@ describe('Model', () => {
     Post.first().should.eql(data[0]);
 
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('last()', () => Post.insert(Array(5).fill({})).then(data => {
     Post.last().should.eql(data[data.length - 1]);
 
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('slice() - no arguments', () => Post.insert(Array(5).fill({})).then(data => {
     Post.slice().data.should.eql(data);
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('slice() - one argument', () => Post.insert(Array(5).fill({})).then(data => {
     Post.slice(2).data.should.eql(data.slice(2));
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('slice() - one negative argument', () => Post.insert(Array(5).fill({})).then(data => {
     Post.slice(-2).data.should.eql(data.slice(-2));
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('slice() - two arguments', () => Post.insert(Array(5).fill({})).then(data => {
     Post.slice(2, 4).data.should.eql(data.slice(2, 4));
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('slice() - start + negative end index', () => Post.insert(Array(5).fill({})).then(data => {
     Post.slice(1, -1).data.should.eql(data.slice(1, -1));
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('slice() - two negative arguments', () => Post.insert(Array(5).fill({})).then(data => {
     Post.slice(-3, -1).data.should.eql(data.slice(-3, -1));
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('slice() - start > end', () => Post.insert(Array(5).fill({})).then(data => {
     Post.slice(-1, -3).data.should.eql(data.slice(-1, -3));
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('slice() - index overflow', () => Post.insert(Array(5).fill({})).then(data => {
     Post.slice(1, 100).data.should.eql(data.slice(1, 100));
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('slice() - index overflow 2', () => Post.insert(Array(5).fill({})).then(data => {
     Post.slice(100, 200).data.should.eql(data.slice(100, 200));
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('limit()', () => Post.insert(Array(5).fill({})).then(data => {
     Post.limit(2).data.should.eql(data.slice(0, 2));
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('skip()', () => Post.insert(Array(5).fill({})).then(data => {
     Post.skip(2).data.should.eql(data.slice(2));
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('reverse()', () => Post.insert(Array(5).fill({})).then(data => {
     const query = Post.reverse();
@@ -804,13 +825,13 @@ describe('Model', () => {
     }
 
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('shuffle()', () => Post.insert(Array(5).fill({})).then(data => {
     const query = Post.shuffle();
     sortBy(query.data, '_id').should.eql(sortBy(data, '_id'));
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('map()', () => Post.insert(Array(5).fill({})).then(data => {
     let num = 0;
@@ -825,75 +846,75 @@ describe('Model', () => {
     d1.should.eql(d2);
 
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('reduce()', () => Post.insert([
-    {email: 'A'},
-    {email: 'B'},
-    {email: 'C'}
+    {title: 'A'},
+    {title: 'B'},
+    {title: 'C'}
   ]).then(data => {
     let num = 1;
 
     const sum = Post.reduce((sum, item, i) => {
       i.should.eql(num++);
-      return {email: sum.email + item.email};
+      return {title: sum.title + item.title};
     });
 
-    sum.email.should.eql('ABC');
+    sum.title.should.eql('ABC');
 
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('reduce() - with initial', () => Post.insert([
-    {email: 'A'},
-    {email: 'B'},
-    {email: 'C'}
+    {title: 'A'},
+    {title: 'B'},
+    {title: 'C'}
   ]).then(data => {
     let num = 0;
 
     const sum = Post.reduce((sum, item, i) => {
       i.should.eql(num++);
-      return sum + item.email;
+      return sum + item.title;
     }, '_');
 
     sum.should.eql('_ABC');
 
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('reduceRight()', () => Post.insert([
-    {email: 'A'},
-    {email: 'B'},
-    {email: 'C'}
+    {title: 'A'},
+    {title: 'B'},
+    {title: 'C'}
   ]).then(data => {
     let num = 1;
 
     const sum = Post.reduceRight((sum, item, i) => {
       i.should.eql(num--);
-      return {email: sum.email + item.email};
+      return {title: sum.title + item.title};
     });
 
-    sum.email.should.eql('CBA');
+    sum.title.should.eql('CBA');
 
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('reduceRight() - with initial', () => Post.insert([
-    {email: 'A'},
-    {email: 'B'},
-    {email: 'C'}
+    {title: 'A'},
+    {title: 'B'},
+    {title: 'C'}
   ]).then(data => {
     let num = 2;
 
     const sum = Post.reduceRight((sum, item, i) => {
       i.should.eql(num--);
-      return sum + item.email;
+      return sum + item.title;
     }, '_');
 
     sum.should.eql('_CBA');
 
     return data;
-  }).map(item => Post.removeById(item._id)));
+  }).map<unknown, any>(item => Post.removeById(item._id)));
 
   it('filter()', () => User.insert([
     {age: 10},
@@ -911,7 +932,7 @@ describe('Model', () => {
     query.data.should.eql(data.slice(2));
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('every()', () => User.insert([
     {age: 10},
@@ -929,7 +950,7 @@ describe('Model', () => {
     User.every((data, i) => data.age > 10).should.be.false;
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('some()', () => User.insert([
     {age: 10},
@@ -947,10 +968,11 @@ describe('Model', () => {
     }).should.be.false;
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('populate() - error', () => {
     try {
+      // @ts-ignore
       Post.populate();
     } catch (err) {
       err.message.should.eql('path is required');
@@ -1230,7 +1252,7 @@ describe('Model', () => {
 
     const Test = db.model('Test', schema);
 
-    Test.add({name: 'foo'}).then(data => {
+    (Test as any).add({name: 'foo'}).then(data => {
       data.name.should.eql('foo');
     });
 
@@ -1299,7 +1321,7 @@ describe('Model', () => {
 
   it('_export() - should not save undefined value', () => {
     // @ts-ignore
-    class CacheType extends SchemaType {
+    class CacheType extends SchemaType<any> {
       value() {}
     }
 
diff --git a/test/scripts/query.ts b/test/scripts/query.ts
index 81192205..af5adaa1 100644
--- a/test/scripts/query.ts
+++ b/test/scripts/query.ts
@@ -5,19 +5,33 @@ const { sortBy } = lodash;
 import Promise from 'bluebird';
 import Document from '../../dist/document';
 import Database from '../../dist/database';
+import type Query from '../../dist/query';
+import type Model from '../../dist/model';
+
+interface UserType {
+  name?: string;
+  age?: number;
+  comments?: string;
+}
+
+interface LoopType {
+  age: {
+    age: number;
+  }
+}
 
 describe('Query', () => {
 
   const db = new Database();
   const Schema = Database.Schema;
 
-  const User = db.model('User', {
+  const User: Model<UserType> = db.model('User', {
     name: String,
     age: Number,
     comments: [{type: Schema.Types.CUID, ref: 'Comment'}]
   });
 
-  const Loop = db.model('Loop', {
+  const Loop: Model<LoopType> = db.model('Loop', {
     age: {
       age: Number
     }
@@ -31,7 +45,7 @@ describe('Query', () => {
   it('count()', () => User.insert(Array(5).fill({})).then(data => {
     User.find({}).count().should.eql(data.length);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('forEach()', () => User.insert(Array(5).fill({})).then(data => {
     let count = 0;
@@ -42,12 +56,12 @@ describe('Query', () => {
     });
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('toArray()', () => User.insert(Array(5).fill({})).then(data => {
     User.find({}).toArray().should.eql(data);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('eq()', () => User.insert(Array(5).fill({})).then(data => {
     const query = User.find({});
@@ -57,7 +71,7 @@ describe('Query', () => {
     }
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('eq() - negative index', () => User.insert(Array(5).fill({})).then(data => {
     const query = User.find({});
@@ -67,42 +81,42 @@ describe('Query', () => {
     }
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('first()', () => User.insert(Array(5).fill({})).then(data => {
     User.find({}).first().should.eql(data[0]);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('last()', () => User.insert(Array(5).fill({})).then(data => {
     User.find({}).last().should.eql(data[data.length - 1]);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('slice()', () => User.insert(Array(5).fill({})).then(data => {
     User.find({}).slice(2, 4).data.should.eql(data.slice(2, 4));
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('limit()', () => User.insert(Array(5).fill({})).then(data => {
     User.find({}).limit(2).data.should.eql(data.slice(0, 2));
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('skip()', () => User.insert(Array(5).fill({})).then(data => {
     User.find({}).skip(2).data.should.eql(data.slice(2));
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('reverse()', () => User.insert(Array(5).fill({})).then(data => {
     User.find({}).reverse().data.should.eql(data.reverse());
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('shuffle()', () => User.insert(Array(5).fill({})).then(data => {
     sortBy(User.find({}).shuffle().data, '_id').should.eql(sortBy(data, '_id'));
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find()', () => User.insert([
     {age: 10},
@@ -120,7 +134,7 @@ describe('Query', () => {
       query.data[i].should.to.be.an.instanceof(Document);
     }
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - blank', () => User.insert([
     {age: 10},
@@ -132,7 +146,7 @@ describe('Query', () => {
     const query = User.find({}).find({});
     query.data.should.eql(data);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - operator', () => User.insert([
     {age: 10},
@@ -143,7 +157,7 @@ describe('Query', () => {
     const query = User.find({}).find({age: {$gt: 20}});
     query.data.should.eql(data.slice(2));
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - limit', () => User.insert([
     {age: 10},
@@ -151,10 +165,10 @@ describe('Query', () => {
     {age: 30},
     {age: 40}
   ]).then(data => {
-    const query = User.find({}).find({age: {$gte: 20}}, {limit: 2});
+    const query = User.find({}).find({age: {$gte: 20}}, {limit: 2}) as Query<UserType>;
     query.data.should.eql(data.slice(1, 3));
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - skip', () => User.insert([
     {age: 10},
@@ -162,15 +176,15 @@ describe('Query', () => {
     {age: 30},
     {age: 40}
   ]).then(data => {
-    let query = User.find({}).find({age: {$gte: 20}}, {skip: 1});
+    let query = User.find({}).find({age: {$gte: 20}}, {skip: 1}) as Query<UserType>;
     query.data.should.eql(data.slice(2));
 
     // with limit
-    query = User.find({}).find({age: {$gte: 20}}, {limit: 1, skip: 1});
+    query = User.find({}).find({age: {$gte: 20}}, {limit: 1, skip: 1}) as Query<UserType>;
     query.data.should.eql(data.slice(2, 3));
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - lean', () => User.insert([
     {age: 10},
@@ -178,14 +192,14 @@ describe('Query', () => {
     {age: 30},
     {age: 40}
   ]).then(data => {
-    const query = User.find({}).find({age: {$gt: 20}}, {lean: true});
+    const query = User.find({}).find({age: {$gt: 20}}, {lean: true}) as Query<UserType>;
     query.should.be.a('array');
     const { length } = query;
     for (let i = 0; i < length; i++) {
       query[i].should.to.not.be.an.instanceof(Document);
     }
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - $and', () => User.insert([
     {name: 'John', age: 20},
@@ -202,7 +216,7 @@ describe('Query', () => {
     query.toArray().should.eql([data[1]]);
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - $or', () => User.insert([
     {name: 'John', age: 20},
@@ -219,7 +233,7 @@ describe('Query', () => {
     query.toArray().should.eql(data.slice(1));
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - $nor', () => User.insert([
     {name: 'John', age: 20},
@@ -236,7 +250,7 @@ describe('Query', () => {
     query.toArray().should.eql([data[0]]);
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - $not', () => User.insert([
     {name: 'John', age: 20},
@@ -250,7 +264,7 @@ describe('Query', () => {
     query.toArray().should.eql([data[2]]);
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - $where', () => User.insert([
     {name: 'John', age: 20},
@@ -266,7 +280,7 @@ describe('Query', () => {
     query.toArray().should.eql(data.slice(0, 2));
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - abnormal - 1', () => User.insert([
     {name: 'John', age: 20},
@@ -282,7 +296,7 @@ describe('Query', () => {
     query.toArray().length.should.eql(0);
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('find() - abnormal - 2', () => User.insert([
     {name: 'John', age: 20},
@@ -298,7 +312,7 @@ describe('Query', () => {
     query.toArray().should.eql([data[2]]);
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('findOne()', () => User.insert([
     {age: 10},
@@ -310,7 +324,7 @@ describe('Query', () => {
     result.should.eql(data[2]);
     result.should.to.be.an.instanceof(Document);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('findOne() - lean', () => User.insert([
     {age: 10},
@@ -318,11 +332,11 @@ describe('Query', () => {
     {age: 30},
     {age: 40}
   ]).then(data => {
-    const result = User.find({}).findOne({age: {$gt: 20}}, {lean: true});
-    result._id.should.eql(data[2]._id);
+    const result = User.find({}).findOne({age: {$gt: 20}}, {lean: true}) as Document<UserType>;
+    result._id!.should.eql(data[2]._id);
     result.should.to.not.be.an.instanceof(Document);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('sort()', () => User.insert([
     {age: 15},
@@ -334,7 +348,7 @@ describe('Query', () => {
     query.data[1].should.eql(data[0]);
     query.data[2].should.eql(data[1]);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('sort() - object', () => Loop.insert([
     {age: {age: 15}},
@@ -346,7 +360,7 @@ describe('Query', () => {
     query.data[1].should.eql(data[0]);
     query.data[2].should.eql(data[1]);
     return data;
-  }).map(item => Loop.removeById(item._id)));
+  }).map<unknown, any>(item => Loop.removeById(item._id)));
 
   it('sort() - descending', () => User.insert([
     {age: 15},
@@ -358,7 +372,7 @@ describe('Query', () => {
     query.data[1].should.eql(data[0]);
     query.data[2].should.eql(data[2]);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('sort() - multi', () => User.insert([
     {age: 15, name: 'A'},
@@ -372,7 +386,7 @@ describe('Query', () => {
     query.data[2].should.eql(data[3]);
     query.data[3].should.eql(data[1]);
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('map()', () => User.insert(Array(5).fill({})).then(data => {
     let num = 0;
@@ -387,7 +401,7 @@ describe('Query', () => {
     d1.should.eql(d2);
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('reduce()', () => User.insert([
     {name: 'A'},
@@ -404,7 +418,7 @@ describe('Query', () => {
     sum.name.should.eql('ABC');
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('reduce() - initial', () => User.insert([
     {name: 'A'},
@@ -421,7 +435,7 @@ describe('Query', () => {
     sum.should.eql('_ABC');
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('reduceRight()', () => User.insert([
     {name: 'A'},
@@ -438,7 +452,7 @@ describe('Query', () => {
     sum.name.should.eql('CBA');
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('reduceRight() - initial', () => User.insert([
     {name: 'A'},
@@ -455,7 +469,7 @@ describe('Query', () => {
     sum.should.eql('_CBA');
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('filter()', () => User.insert([
     {age: 10},
@@ -473,7 +487,7 @@ describe('Query', () => {
     query.data.should.eql(data.slice(2));
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('every()', () => User.insert([
     {age: 10},
@@ -491,7 +505,7 @@ describe('Query', () => {
     User.find({}).every((data, i) => data.age > 10).should.be.false;
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('some()', () => User.insert([
     {age: 10},
@@ -509,7 +523,7 @@ describe('Query', () => {
     }).should.be.false;
 
     return data;
-  }).map(item => User.removeById(item._id)));
+  }).map<unknown, any>(item => User.removeById(item._id)));
 
   it('update()', () => User.insert([
     {age: 10},
@@ -523,7 +537,7 @@ describe('Query', () => {
     updated[0].name.should.eql('A');
     updated[1].name.should.eql('A');
     return data;
-  })).map(item => User.removeById(item._id)));
+  })).map<unknown, any>(item => User.removeById(item._id)));
 
   it('replace()', () => User.insert([
     {age: 10},
@@ -537,7 +551,7 @@ describe('Query', () => {
     updated[0].name.should.eql('A');
     updated[1].name.should.eql('A');
     return data;
-  })).map(item => User.removeById(item._id)));
+  })).map<unknown, any>(item => User.removeById(item._id)));
 
   it('remove()', () => User.insert([
     {age: 10},
@@ -549,7 +563,7 @@ describe('Query', () => {
     should.not.exist(User.findById(data[1]._id));
     should.not.exist(User.findById(data[3]._id));
     return [data[0], data[2], data[4]];
-  })).map(item => User.removeById(item._id)));
+  })).map<unknown, any>(item => User.removeById(item._id)));
 
   it('populate() - object', () => {
     let user, comment;
diff --git a/test/scripts/schema.ts b/test/scripts/schema.ts
index 2a4f9a70..dbe04a8f 100644
--- a/test/scripts/schema.ts
+++ b/test/scripts/schema.ts
@@ -100,9 +100,11 @@ describe('Schema', () => {
     schema.hooks.pre.remove.should.have.length(1);
 
     // incompatible type
+    // @ts-ignore
     (() => schema.pre('wtf', () => {})).should.to.throw(TypeError, 'Hook type must be `save` or `remove`!');
 
     // hook is not a function
+    // @ts-ignore
     (() => schema.pre('save', {})).should.to.throw(TypeError, 'Hook must be a function!');
   });
 
@@ -120,9 +122,11 @@ describe('Schema', () => {
     schema.hooks.post.remove.should.have.length(1);
 
     // incompatible type
+    // @ts-ignore
     (() => schema.post('wtf', () => {})).should.throw(TypeError, 'Hook type must be `save` or `remove`!');
 
     // hook is not a function
+    // @ts-ignore
     (() => schema.post('save', {})).should.to.throw(TypeError, 'Hook must be a function!');
   });
 
@@ -137,6 +141,7 @@ describe('Schema', () => {
     schema.method.should.to.throw(TypeError, 'Method name is required!');
 
     // without function
+    // @ts-ignore
     (() => schema.method('wtf', {})).should.to.throw(TypeError, 'Instance method must be a function!');
   });
 
@@ -151,6 +156,7 @@ describe('Schema', () => {
     schema.static.should.to.throw(TypeError, 'Method name is required!');
 
     // without function
+    // @ts-ignore
     (() => schema.static('wtf', {})).should.to.throw(TypeError, 'Static method must be a function!');
   });
 });
diff --git a/test/scripts/schematype.ts b/test/scripts/schematype.ts
index a49090e5..39abb55f 100644
--- a/test/scripts/schematype.ts
+++ b/test/scripts/schematype.ts
@@ -4,24 +4,24 @@ import ValidationError from '../../dist/error/validation';
 import SchemaType from '../../dist/schematype';
 
 describe('SchemaType', () => {
-  const type = new SchemaType('test');
+  const type = new SchemaType<number>('test');
 
   it('cast()', () => {
-    type.cast(123).should.eql(123);
+    (type.cast(123) as number).should.eql(123);
   });
 
   it('cast() - default', () => {
     const type = new SchemaType('test', {default: 'foo'});
-    type.cast().should.eql('foo');
+    (type.cast() as string).should.eql('foo');
   });
 
   it('cast() - default - function', () => {
     const type = new SchemaType('test', {default: () => 'foo'});
-    type.cast().should.eql('foo');
+    (type.cast() as string).should.eql('foo');
   });
 
   it('validate()', () => {
-    type.validate(123).should.eql(123);
+    (type.validate(123) as number).should.eql(123);
   });
 
   it('validate() - required', () => {
@@ -127,12 +127,12 @@ describe('SchemaType', () => {
   });
 
   it('u$set', () => {
-    type.u$set(1, 1).should.eql(1);
+    type.u$set<number>(1, 1).should.eql(1);
   });
 
   it('u$unset', () => {
     should.not.exist(type.u$unset(1, true));
-    type.u$unset(1, false).should.eql(1);
+    (type.u$unset<number>(1, false) as number).should.eql(1);
   });
 
   it('u$rename', () => {
diff --git a/test/scripts/types/array.ts b/test/scripts/types/array.ts
index 19ba5313..61cd52ba 100644
--- a/test/scripts/types/array.ts
+++ b/test/scripts/types/array.ts
@@ -13,12 +13,12 @@ describe('SchemaTypeArray', () => {
     type.cast('foo').should.eql(['foo']);
     type.cast([]).should.eql([]);
     type.cast([1, 2, 3]).should.eql([1, 2, 3]);
-    type.cast().should.eql([]);
+    (type.cast() as any[]).should.eql([]);
   });
 
   it('cast() - default', () => {
     const type = new SchemaTypeArray('test', {default: [1, 2, 3]});
-    type.cast().should.eql([1, 2, 3]);
+    (type.cast() as any[]).should.eql([1, 2, 3]);
   });
 
   it('cast() - child', () => {
diff --git a/test/scripts/types/buffer.ts b/test/scripts/types/buffer.ts
index 9bae4b19..90ee44c9 100644
--- a/test/scripts/types/buffer.ts
+++ b/test/scripts/types/buffer.ts
@@ -25,7 +25,7 @@ describe('SchemaTypeBuffer', () => {
     const buf = Buffer.from([97, 98, 99]);
     const type = new SchemaTypeBuffer('test', {default: buf});
 
-    type.cast().should.eql(buf);
+    (type.cast() as Buffer).should.eql(buf);
   });
 
   function shouldThrowError(value) {
@@ -50,7 +50,9 @@ describe('SchemaTypeBuffer', () => {
   it('match()', () => {
     type.match(Buffer.from([97, 98, 99]), Buffer.from([97, 98, 99])).should.be.true;
     type.match(Buffer.from([97, 98, 99]), Buffer.from([97, 98, 100])).should.be.false;
+    // @ts-ignore
     type.match(undefined, Buffer.from([97, 98, 99])).should.be.false;
+    // @ts-ignore
     type.match(undefined, undefined).should.be.true;
   });
 
diff --git a/test/scripts/types/date.ts b/test/scripts/types/date.ts
index da80826b..49a55ca3 100644
--- a/test/scripts/types/date.ts
+++ b/test/scripts/types/date.ts
@@ -16,7 +16,7 @@ describe('SchemaTypeDate', () => {
     const date = new Date();
     const type = new SchemaTypeDate('test', {default: date});
 
-    type.cast().should.eql(date);
+    (type.cast() as Date).should.eql(date);
   });
 
   function shouldThrowError(value) {
@@ -42,7 +42,9 @@ describe('SchemaTypeDate', () => {
   it('match()', () => {
     type.match(new Date(2014, 1, 1), new Date(2014, 1, 1)).should.be.true;
     type.match(new Date(2014, 1, 1), new Date(2014, 1, 2)).should.be.false;
+    // @ts-ignore
     type.match(undefined, new Date()).should.be.false;
+    // @ts-ignore
     type.match(undefined, undefined).should.be.true;
   });
 
diff --git a/test/scripts/types/enum.ts b/test/scripts/types/enum.ts
index ded35ace..7804322b 100644
--- a/test/scripts/types/enum.ts
+++ b/test/scripts/types/enum.ts
@@ -7,7 +7,7 @@ describe('SchemaTypeEnum', () => {
   it('validate()', () => {
     const type = new SchemaTypeEnum('test', {elements: ['foo', 'bar', 'baz']});
 
-    type.validate('foo').should.eql('foo');
+    (type.validate('foo') as string).should.eql('foo');
 
     (() => type.validate('wat')).should.to.throw(ValidationError, 'The value must be one of foo, bar, baz');
   });
diff --git a/test/scripts/types/number.ts b/test/scripts/types/number.ts
index ae56afbf..3dd6003b 100644
--- a/test/scripts/types/number.ts
+++ b/test/scripts/types/number.ts
@@ -17,7 +17,7 @@ describe('SchemaTypeNumber', () => {
 
   it('cast() - default', () => {
     const type = new SchemaTypeNumber('type', {default: 42});
-    type.cast().should.eql(42);
+    (type.cast() as number).should.eql(42);
   });
 
   function shouldThrowError(value) {
diff --git a/test/scripts/types/object.ts b/test/scripts/types/object.ts
index e29b6473..960b651c 100644
--- a/test/scripts/types/object.ts
+++ b/test/scripts/types/object.ts
@@ -6,6 +6,6 @@ describe('SchemaTypeObject', () => {
   const type = new SchemaTypeObject('test');
 
   it('cast() - default', () => {
-    type.cast().should.eql({});
+    (type.cast() as object).should.eql({});
   });
 });
diff --git a/test/scripts/types/string.ts b/test/scripts/types/string.ts
index b2572c8c..ebbda208 100644
--- a/test/scripts/types/string.ts
+++ b/test/scripts/types/string.ts
@@ -21,7 +21,7 @@ describe('SchemaTypeString', () => {
 
   it('cast() - default', () => {
     const type = new SchemaTypeString('test', {default: 'foo'});
-    type.cast().should.eql('foo');
+    (type.cast() as string).should.eql('foo');
   });
 
   function shouldThrowError(value) {
diff --git a/test/scripts/types/virtual.ts b/test/scripts/types/virtual.ts
index ddbc83c5..0d4880db 100644
--- a/test/scripts/types/virtual.ts
+++ b/test/scripts/types/virtual.ts
@@ -9,10 +9,11 @@ describe('SchemaTypeVirtual', () => {
     const getter = () => 'foo';
 
     type.get(getter);
-    type.getter.should.eql(getter);
+    (type.getter as () => any).should.eql(getter);
   });
 
   it('get() - type check', () => {
+    // @ts-ignore
     (() => type.get(123)).should.to.throw(TypeError, 'Getter must be a function!');
   });
 
@@ -22,10 +23,11 @@ describe('SchemaTypeVirtual', () => {
     };
 
     type.set(setter);
-    type.setter.should.eql(setter);
+    (type.setter as () => any).should.eql(setter);
   });
 
   it('set() - type check', () => {
+    // @ts-ignore
     (() => type.set(123)).should.to.throw(TypeError, 'Setter must be a function!');
   });