diff --git a/.github/workflows/linux-tests.yml b/.github/workflows/linux-tests.yml
index 436040c..1aa2c9e 100644
--- a/.github/workflows/linux-tests.yml
+++ b/.github/workflows/linux-tests.yml
@@ -8,7 +8,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [10.x, 12.x, 18.x, 20.x, 22.x]
+        node-version: [18.x, 20.x, 22.x]
 
     steps:
     - name: Checkout Project
diff --git a/.github/workflows/windows-tests.yml b/.github/workflows/windows-tests.yml
index be4526b..8bcb1b4 100644
--- a/.github/workflows/windows-tests.yml
+++ b/.github/workflows/windows-tests.yml
@@ -9,7 +9,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [10.x, 12.x, 18.x, 20.x, 22.x]
+        node-version: [18.x, 20.x, 22.x]
 
     steps:
     - name: Checkout Project
diff --git a/dist/env-cmd.d.ts b/dist/env-cmd.d.ts
index 859a7da..5141864 100644
--- a/dist/env-cmd.d.ts
+++ b/dist/env-cmd.d.ts
@@ -5,9 +5,7 @@ import { EnvCmdOptions } from './types';
  * @param {string[]} args Command line argument to pass in ['-f', './.env']
  * @returns {Promise<{ [key: string]: any }>}
  */
-export declare function CLI(args: string[]): Promise<{
-    [key: string]: any;
-}>;
+export declare function CLI(args: string[]): Promise<Record<string, any>>;
 /**
  * The main env-cmd program. This will spawn a new process and run the given command using
  * various environment file solutions.
@@ -16,6 +14,4 @@ export declare function CLI(args: string[]): Promise<{
  * @param {EnvCmdOptions} { command, commandArgs, envFile, rc, options }
  * @returns {Promise<{ [key: string]: any }>} Returns an object containing [environment variable name]: value
  */
-export declare function EnvCmd({ command, commandArgs, envFile, rc, options }: EnvCmdOptions): Promise<{
-    [key: string]: any;
-}>;
+export declare function EnvCmd({ command, commandArgs, envFile, rc, options }: EnvCmdOptions): Promise<Record<string, any>>;
diff --git a/dist/expand-envs.d.ts b/dist/expand-envs.d.ts
index cd06ffa..5a68b32 100644
--- a/dist/expand-envs.d.ts
+++ b/dist/expand-envs.d.ts
@@ -2,6 +2,4 @@
  * expandEnvs Replaces $var in args and command with environment variables
  * the environment variable doesn't exist, it leaves it as is.
 */
-export declare function expandEnvs(str: string, envs: {
-    [key: string]: any;
-}): string;
+export declare function expandEnvs(str: string, envs: Record<string, any>): string;
diff --git a/dist/get-env-vars.d.ts b/dist/get-env-vars.d.ts
index dc7ea2c..aaf968e 100644
--- a/dist/get-env-vars.d.ts
+++ b/dist/get-env-vars.d.ts
@@ -1,18 +1,12 @@
 import { GetEnvVarOptions } from './types';
-export declare function getEnvVars(options?: GetEnvVarOptions): Promise<{
-    [key: string]: any;
-}>;
+export declare function getEnvVars(options?: GetEnvVarOptions): Promise<Record<string, any>>;
 export declare function getEnvFile({ filePath, fallback, verbose }: {
     filePath?: string;
     fallback?: boolean;
     verbose?: boolean;
-}): Promise<{
-    [key: string]: any;
-}>;
+}): Promise<Record<string, any>>;
 export declare function getRCFile({ environments, filePath, verbose }: {
     environments: string[];
     filePath?: string;
     verbose?: boolean;
-}): Promise<{
-    [key: string]: any;
-}>;
+}): Promise<Record<string, any>>;
diff --git a/dist/parse-args.js b/dist/parse-args.js
index 5e1f894..c650ea5 100644
--- a/dist/parse-args.js
+++ b/dist/parse-args.js
@@ -3,7 +3,7 @@ Object.defineProperty(exports, "__esModule", { value: true });
 const commander = require("commander");
 const utils_1 = require("./utils");
 // Use commonjs require to prevent a weird folder hierarchy in dist
-const packageJson = require('../package.json'); /* eslint-disable-line */
+const packageJson = require('../package.json');  
 /**
 * Parses the arguments passed into the cli
 */
diff --git a/dist/parse-env-file.d.ts b/dist/parse-env-file.d.ts
index 530f487..c298868 100644
--- a/dist/parse-env-file.d.ts
+++ b/dist/parse-env-file.d.ts
@@ -1,21 +1,15 @@
 /**
  * Gets the environment vars from an env file
  */
-export declare function getEnvFileVars(envFilePath: string): Promise<{
-    [key: string]: any;
-}>;
+export declare function getEnvFileVars(envFilePath: string): Promise<Record<string, any>>;
 /**
  * Parse out all env vars from a given env file string and return an object
  */
-export declare function parseEnvString(envFileString: string): {
-    [key: string]: string;
-};
+export declare function parseEnvString(envFileString: string): Record<string, string>;
 /**
  * Parse out all env vars from an env file string
  */
-export declare function parseEnvVars(envString: string): {
-    [key: string]: string;
-};
+export declare function parseEnvVars(envString: string): Record<string, string>;
 /**
  * Strips out comments from env file string
  */
diff --git a/dist/parse-env-file.js b/dist/parse-env-file.js
index 6b6dafe..a4370ce 100644
--- a/dist/parse-env-file.js
+++ b/dist/parse-env-file.js
@@ -18,7 +18,7 @@ async function getEnvFileVars(envFilePath) {
     const ext = path.extname(absolutePath).toLowerCase();
     let env = {};
     if (REQUIRE_HOOK_EXTENSIONS.includes(ext)) {
-        const possiblePromise = require(absolutePath); /* eslint-disable-line */
+        const possiblePromise = require(absolutePath);  
         env = utils_1.isPromise(possiblePromise) ? await possiblePromise : possiblePromise;
     }
     else {
diff --git a/dist/parse-rc-file.d.ts b/dist/parse-rc-file.d.ts
index 053adf2..bd193e1 100644
--- a/dist/parse-rc-file.d.ts
+++ b/dist/parse-rc-file.d.ts
@@ -4,6 +4,4 @@
 export declare function getRCFileVars({ environments, filePath }: {
     environments: string[];
     filePath: string;
-}): Promise<{
-    [key: string]: any;
-}>;
+}): Promise<Record<string, any>>;
diff --git a/dist/parse-rc-file.js b/dist/parse-rc-file.js
index f3df690..07bb65e 100644
--- a/dist/parse-rc-file.js
+++ b/dist/parse-rc-file.js
@@ -24,7 +24,7 @@ async function getRCFileVars({ environments, filePath }) {
     let parsedData;
     try {
         if (ext === '.json' || ext === '.js' || ext === '.cjs') {
-            const possiblePromise = require(absolutePath); /* eslint-disable-line */
+            const possiblePromise = require(absolutePath);  
             parsedData = utils_1.isPromise(possiblePromise) ? await possiblePromise : possiblePromise;
         }
         else {
diff --git a/dist/utils.d.ts b/dist/utils.d.ts
index d3714a7..9a731d9 100644
--- a/dist/utils.d.ts
+++ b/dist/utils.d.ts
@@ -9,4 +9,4 @@ export declare function parseArgList(list: string): string[];
 /**
  * A simple function to test if the value is a promise
  */
-export declare function isPromise(value: any | PromiseLike<Object>): value is Promise<any>;
+export declare function isPromise(value: any | PromiseLike<object>): value is Promise<any>;
diff --git a/eslint.config.js b/eslint.config.js
new file mode 100644
index 0000000..9edb080
--- /dev/null
+++ b/eslint.config.js
@@ -0,0 +1,43 @@
+const eslint = require('@eslint/js')
+const tseslint = require('typescript-eslint')
+const globals = require('globals')
+const stylistic = require('@stylistic/eslint-plugin')
+
+module.exports = tseslint.config(
+  {
+    ignores: ['dist/*', 'bin/*'],
+    rules: {
+      '@typescript-eslint/no-require-imports': 'off',
+    },
+    languageOptions: {
+      globals: {
+        ...globals.node,
+      },
+      parserOptions: {
+        projectService: {
+          allowDefaultProject: ['test/*.ts'],
+        },
+      },
+    },
+    extends: [
+      eslint.configs.recommended,
+      stylistic.configs['recommended-flat'],
+      tseslint.configs.strictTypeChecked,
+      tseslint.configs.stylisticTypeChecked,
+    ],
+  },
+  // Disable Type Checking JS files
+  {
+    files: ['**/*.js'],
+    extends: [tseslint.configs.disableTypeChecked],
+  },
+  {
+    // For test files ignore some rules
+    files: ['test/*.ts'],
+    rules: {
+      '@typescript-eslint/no-explicit-any': 'off',
+      '@typescript-eslint/no-unsafe-member-access': 'off',
+      '@typescript-eslint/no-unsafe-assignment': 'off',
+    },
+  },
+)
diff --git a/eslint.config.js.test b/eslint.config.js.test
new file mode 100644
index 0000000..00e63e2
--- /dev/null
+++ b/eslint.config.js.test
@@ -0,0 +1,26 @@
+module.exports = (async function config() {
+  const { default: love } = await import('eslint-config-love')
+
+  return [
+    love,
+    {
+      files: [
+        'src/**/*.[j|t]s', 
+        // 'src/**/*.ts',
+        'test/**/*.[j|t]s',
+        // 'test/**/*.ts'
+      ],
+      languageOptions: {
+        parserOptions: {
+          projectService: {
+            allowDefaultProject: ['eslint.config.js', 'bin/env-cmd.js'],
+            defaultProject: './tsconfig.json',
+          },
+        },
+      },
+    },
+    {
+      ignores: ['dist/'],
+    }
+  ]
+})()
diff --git a/package.json b/package.json
index 99ef782..4c8ace4 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "env-cmd",
-  "version": "10.1.0",
+  "version": "10.2.0",
   "description": "Executes a command using the environment variables in an env file",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",
@@ -14,7 +14,7 @@
     "test": "mocha -r ts-node/register ./test/**/*.ts",
     "test-cover": "nyc npm test",
     "coveralls": "coveralls < coverage/lcov.info",
-    "lint": "ts-standard --fix && tsc --noEmit",
+    "lint": "npx eslint .",
     "build": "tsc",
     "watch": "tsc -w"
   },
@@ -53,6 +53,8 @@
   "devDependencies": {
     "@commitlint/cli": "^8.0.0",
     "@commitlint/config-conventional": "^8.0.0",
+    "@eslint/js": "^9.15.0",
+    "@stylistic/eslint-plugin": "^2.11.0",
     "@types/chai": "^4.0.0",
     "@types/cross-spawn": "^6.0.0",
     "@types/mocha": "^7.0.0",
@@ -60,13 +62,14 @@
     "@types/sinon": "^9.0.0",
     "chai": "^4.0.0",
     "coveralls": "^3.0.0",
+    "globals": "^15.12.0",
     "husky": "^4.0.0",
     "mocha": "^7.0.0",
     "nyc": "^15.0.0",
     "sinon": "^9.0.0",
     "ts-node": "^8.0.0",
-    "ts-standard": "^8.0.0",
-    "typescript": "^5.7.2"
+    "typescript": "^5.7.2",
+    "typescript-eslint": "^8.15.0"
   },
   "nyc": {
     "include": [
@@ -85,12 +88,6 @@
     "sourceMap": true,
     "instrument": true
   },
-  "ts-standard": {
-    "project": "./tsconfig.eslint.json",
-    "ignore": [
-      "dist"
-    ]
-  },
   "greenkeeper": {
     "ignore": [
       "@types/node"
diff --git a/src/env-cmd.ts b/src/env-cmd.ts
index cc3179a..424998b 100644
--- a/src/env-cmd.ts
+++ b/src/env-cmd.ts
@@ -1,5 +1,5 @@
 import { spawn } from './spawn'
-import { EnvCmdOptions } from './types'
+import { EnvCmdOptions, Environment } from './types'
 import { TermSignals } from './signal-termination'
 import { parseArgs } from './parse-args'
 import { getEnvVars } from './get-env-vars'
@@ -9,16 +9,17 @@ import { expandEnvs } from './expand-envs'
  * Executes env - cmd using command line arguments
  * @export
  * @param {string[]} args Command line argument to pass in ['-f', './.env']
- * @returns {Promise<{ [key: string]: any }>}
+ * @returns {Promise<Environment>}
  */
-export async function CLI (args: string[]): Promise<{ [key: string]: any }> {
+export async function CLI(args: string[]): Promise<Environment> {
   // Parse the args from the command line
   const parsedArgs = parseArgs(args)
 
   // Run EnvCmd
   try {
-    return await (exports.EnvCmd(parsedArgs) as Promise<{ [key: string]: any }>)
-  } catch (e) {
+    return await (exports as { EnvCmd: typeof EnvCmd }).EnvCmd(parsedArgs)
+  }
+  catch (e) {
     console.error(e)
     return process.exit(1)
   }
@@ -30,21 +31,22 @@ export async function CLI (args: string[]): Promise<{ [key: string]: any }> {
  *
  * @export
  * @param {EnvCmdOptions} { command, commandArgs, envFile, rc, options }
- * @returns {Promise<{ [key: string]: any }>} Returns an object containing [environment variable name]: value
+ * @returns {Promise<Environment>} Returns an object containing [environment variable name]: value
  */
-export async function EnvCmd (
+export async function EnvCmd(
   {
     command,
     commandArgs,
     envFile,
     rc,
-    options = {}
-  }: EnvCmdOptions
-): Promise<{ [key: string]: any }> {
-  let env: { [name: string]: string } = {}
+    options = {},
+  }: EnvCmdOptions,
+): Promise<Environment> {
+  let env: Environment = {}
   try {
     env = await getEnvVars({ envFile, rc, verbose: options.verbose })
-  } catch (e) {
+  }
+  catch (e) {
     if (!(options.silent ?? false)) {
       throw e
     }
@@ -52,7 +54,8 @@ export async function EnvCmd (
   // Override the merge order if --no-override flag set
   if (options.noOverride === true) {
     env = Object.assign({}, env, process.env)
-  } else {
+  }
+  else {
     // Add in the system environment variables to our environment list
     env = Object.assign({}, process.env, env)
   }
@@ -66,7 +69,7 @@ export async function EnvCmd (
   const proc = spawn(command, commandArgs, {
     stdio: 'inherit',
     shell: options.useShell,
-    env
+    env: env as Record<string, string>,
   })
 
   // Handle any termination signals for parent and child proceses
diff --git a/src/expand-envs.ts b/src/expand-envs.ts
index cd77317..f3c3b3a 100644
--- a/src/expand-envs.ts
+++ b/src/expand-envs.ts
@@ -1,11 +1,13 @@
+import { Environment } from './types'
 
 /**
  * expandEnvs Replaces $var in args and command with environment variables
- * the environment variable doesn't exist, it leaves it as is.
+ * if the environment variable doesn't exist, it leaves it as is.
 */
-export function expandEnvs (str: string, envs: { [key: string]: any }): string {
-  return str.replace(/(?<!\\)\$[a-zA-Z0-9_]+/g, varName => {
+export function expandEnvs(str: string, envs: Environment): string {
+  return str.replace(/(?<!\\)\$[a-zA-Z0-9_]+/g, (varName) => {
     const varValue = envs[varName.slice(1)]
-    return varValue === undefined ? varName : varValue
+    // const test = 42;
+    return varValue === undefined ? varName : varValue.toString()
   })
 }
diff --git a/src/get-env-vars.ts b/src/get-env-vars.ts
index cd5db92..e4e6b8d 100644
--- a/src/get-env-vars.ts
+++ b/src/get-env-vars.ts
@@ -1,30 +1,30 @@
-import { GetEnvVarOptions } from './types'
+import { GetEnvVarOptions, Environment } from './types'
 import { getRCFileVars } from './parse-rc-file'
 import { getEnvFileVars } from './parse-env-file'
 
 const RC_FILE_DEFAULT_LOCATIONS = ['./.env-cmdrc', './.env-cmdrc.js', './.env-cmdrc.json']
 const ENV_FILE_DEFAULT_LOCATIONS = ['./.env', './.env.js', './.env.json']
 
-export async function getEnvVars (options: GetEnvVarOptions = {}): Promise<{ [key: string]: any }> {
-  options.envFile = options.envFile !== undefined ? options.envFile : {}
+export async function getEnvVars(options: GetEnvVarOptions = {}): Promise<Environment> {
+  options.envFile = options.envFile ?? {}
   // Check for rc file usage
   if (options.rc !== undefined) {
     return await getRCFile({
       environments: options.rc.environments,
       filePath: options.rc.filePath,
-      verbose: options.verbose
+      verbose: options.verbose,
     })
   }
   return await getEnvFile({
     filePath: options.envFile.filePath,
     fallback: options.envFile.fallback,
-    verbose: options.verbose
+    verbose: options.verbose,
   })
 }
 
-export async function getEnvFile (
-  { filePath, fallback, verbose }: { filePath?: string, fallback?: boolean, verbose?: boolean }
-): Promise<{ [key: string]: any }> {
+export async function getEnvFile(
+  { filePath, fallback, verbose }: { filePath?: string, fallback?: boolean, verbose?: boolean },
+): Promise<Environment> {
   // Use env file
   if (filePath !== undefined) {
     try {
@@ -33,10 +33,12 @@ export async function getEnvFile (
         console.info(`Found .env file at path: ${filePath}`)
       }
       return env
-    } catch (e) {
+    }
+    catch {
       if (verbose === true) {
         console.info(`Failed to find .env file at path: ${filePath}`)
       }
+      // Ignore error as we are just trying this location
     }
     if (fallback !== true) {
       throw new Error(`Failed to find .env file at path: ${filePath}`)
@@ -51,7 +53,10 @@ export async function getEnvFile (
         console.info(`Found .env file at default path: ${path}`)
       }
       return env
-    } catch (e) { }
+    }
+    catch {
+      // Ignore error because we are just trying this location
+    }
   }
 
   const error = `Failed to find .env file at default paths: [${ENV_FILE_DEFAULT_LOCATIONS.join(',')}]`
@@ -61,9 +66,9 @@ export async function getEnvFile (
   throw new Error(error)
 }
 
-export async function getRCFile (
-  { environments, filePath, verbose }: { environments: string[], filePath?: string, verbose?: boolean }
-): Promise<{ [key: string]: any }> {
+export async function getRCFile(
+  { environments, filePath, verbose }: { environments: string[], filePath?: string, verbose?: boolean },
+): Promise<Environment> {
   // User provided an .rc file path
   if (filePath !== undefined) {
     try {
@@ -72,15 +77,18 @@ export async function getRCFile (
         console.info(`Found environments: [${environments.join(',')}] for .rc file at path: ${filePath}`)
       }
       return env
-    } catch (e) {
-      if (e.name === 'PathError') {
-        if (verbose === true) {
-          console.info(`Failed to find .rc file at path: ${filePath}`)
+    }
+    catch (e) {
+      if (e instanceof Error) {
+        if (e.name === 'PathError') {
+          if (verbose === true) {
+            console.info(`Failed to find .rc file at path: ${filePath}`)
+          }
         }
-      }
-      if (e.name === 'EnvironmentError') {
-        if (verbose === true) {
-          console.info(`Failed to find environments: [${environments.join(',')}] for .rc file at path: ${filePath}`)
+        if (e.name === 'EnvironmentError') {
+          if (verbose === true) {
+            console.info(`Failed to find environments: [${environments.join(',')}] for .rc file at path: ${filePath}`)
+          }
         }
       }
       throw e
@@ -95,19 +103,22 @@ export async function getRCFile (
         console.info(`Found environments: [${environments.join(',')}] for default .rc file at path: ${path}`)
       }
       return env
-    } catch (e) {
-      if (e.name === 'EnvironmentError') {
-        const errorText = `Failed to find environments: [${environments.join(',')}] for .rc file at path: ${path}`
-        if (verbose === true) {
-          console.info(errorText)
+    }
+    catch (e) {
+      if (e instanceof Error) {
+        if (e.name === 'EnvironmentError') {
+          const errorText = `Failed to find environments: [${environments.join(',')}] for .rc file at path: ${path}`
+          if (verbose === true) {
+            console.info(errorText)
+          }
+          throw new Error(errorText)
         }
-        throw new Error(errorText)
-      }
-      if (e.name === 'ParseError') {
-        if (verbose === true) {
-          console.info(e.message)
+        if (e.name === 'ParseError') {
+          if (verbose === true) {
+            console.info(e.message)
+          }
+          throw new Error(e.message)
         }
-        throw new Error(e.message)
       }
     }
   }
diff --git a/src/parse-args.ts b/src/parse-args.ts
index bbd4c56..cdf0927 100644
--- a/src/parse-args.ts
+++ b/src/parse-args.ts
@@ -1,14 +1,14 @@
 import * as commander from 'commander'
-import { EnvCmdOptions } from './types'
+import { EnvCmdOptions, CommanderOptions, EnvFileOptions, RCFileOptions } from './types'
 import { parseArgList } from './utils'
 
 // Use commonjs require to prevent a weird folder hierarchy in dist
-const packageJson = require('../package.json') /* eslint-disable-line */
+const packageJson: { version: string } = require('../package.json') /* eslint-disable-line */
 
 /**
 * Parses the arguments passed into the cli
 */
-export function parseArgs (args: string[]): EnvCmdOptions {
+export function parseArgs(args: string[]): EnvCmdOptions {
   // Run the initial arguments through commander in order to determine
   // which value in the args array is the `command` to execute
   let program = parseArgsUsingCommander(args)
@@ -42,23 +42,27 @@ export function parseArgs (args: string[]): EnvCmdOptions {
     silent = true
   }
 
-  let rc: any
-  if (program.environments !== undefined && program.environments.length !== 0) {
+  let rc: RCFileOptions | undefined
+  if (
+    program.environments !== undefined
+    && Array.isArray(program.environments)
+    && program.environments.length !== 0
+  ) {
     rc = {
       environments: program.environments,
-      filePath: program.rcFile
+      filePath: program.rcFile,
     }
   }
 
-  let envFile: any
+  let envFile: EnvFileOptions | undefined
   if (program.file !== undefined) {
     envFile = {
       filePath: program.file,
-      fallback: program.fallback
+      fallback: program.fallback,
     }
   }
 
-  const options = {
+  const options: EnvCmdOptions = {
     command,
     commandArgs,
     envFile,
@@ -68,8 +72,8 @@ export function parseArgs (args: string[]): EnvCmdOptions {
       noOverride,
       silent,
       useShell,
-      verbose
-    }
+      verbose,
+    },
   }
   if (verbose) {
     console.info(`Options: ${JSON.stringify(options, null, 0)}`)
@@ -77,8 +81,8 @@ export function parseArgs (args: string[]): EnvCmdOptions {
   return options
 }
 
-export function parseArgsUsingCommander (args: string[]): commander.Command {
-  const program = new commander.Command()
+export function parseArgsUsingCommander(args: string[]): CommanderOptions {
+  const program = new commander.Command() as CommanderOptions
   return program
     .version(packageJson.version, '-v, --version')
     .usage('[options] <command> [...args]')
diff --git a/src/parse-env-file.ts b/src/parse-env-file.ts
index bbd6334..488da52 100644
--- a/src/parse-env-file.ts
+++ b/src/parse-env-file.ts
@@ -1,13 +1,14 @@
 import * as fs from 'fs'
 import * as path from 'path'
 import { resolveEnvFilePath, isPromise } from './utils'
+import { Environment } from './types'
 
 const REQUIRE_HOOK_EXTENSIONS = ['.json', '.js', '.cjs']
 
 /**
  * Gets the environment vars from an env file
  */
-export async function getEnvFileVars (envFilePath: string): Promise<{ [key: string]: any }> {
+export async function getEnvFileVars(envFilePath: string): Promise<Environment> {
   const absolutePath = resolveEnvFilePath(envFilePath)
   if (!fs.existsSync(absolutePath)) {
     const pathError = new Error(`Invalid env file path (${envFilePath}).`)
@@ -17,11 +18,12 @@ export async function getEnvFileVars (envFilePath: string): Promise<{ [key: stri
 
   // Get the file extension
   const ext = path.extname(absolutePath).toLowerCase()
-  let env = {}
+  let env: Environment = {}
   if (REQUIRE_HOOK_EXTENSIONS.includes(ext)) {
-    const possiblePromise = require(absolutePath) /* eslint-disable-line */
+    const possiblePromise: Environment | Promise<Environment> = require(absolutePath) /* eslint-disable-line */
     env = isPromise(possiblePromise) ? await possiblePromise : possiblePromise
-  } else {
+  }
+  else {
     const file = fs.readFileSync(absolutePath, { encoding: 'utf8' })
     env = parseEnvString(file)
   }
@@ -31,7 +33,7 @@ export async function getEnvFileVars (envFilePath: string): Promise<{ [key: stri
 /**
  * Parse out all env vars from a given env file string and return an object
  */
-export function parseEnvString (envFileString: string): { [key: string]: string } {
+export function parseEnvString(envFileString: string): Environment {
   // First thing we do is stripe out all comments
   envFileString = stripComments(envFileString.toString())
 
@@ -45,27 +47,41 @@ export function parseEnvString (envFileString: string): { [key: string]: string
 /**
  * Parse out all env vars from an env file string
  */
-export function parseEnvVars (envString: string): { [key: string]: string } {
+export function parseEnvVars(envString: string): Environment {
   const envParseRegex = /^((.+?)[=](.*))$/gim
-  const matches: { [key: string]: string } = {}
+  const matches: Environment = {}
   let match
   while ((match = envParseRegex.exec(envString)) !== null) {
     // Note: match[1] is the full env=var line
     const key = match[2].trim()
-    const value = match[3].trim()
+    let value: string | number | boolean = match[3].trim()
 
     // remove any surrounding quotes
-    matches[key] = value
+    value = value
       .replace(/(^['"]|['"]$)/g, '')
       .replace(/\\n/g, '\n')
+
+    // Convert string to JS type if appropriate
+    if (value !== '' && !isNaN(+value)) {
+      matches[key] = +value
+    }
+    else if (value === 'true') {
+      matches[key] = true
+    }
+    else if (value === 'false') {
+      matches[key] = false
+    }
+    else {
+      matches[key] = value
+    }
   }
-  return matches
+  return JSON.parse(JSON.stringify(matches)) as Environment
 }
 
 /**
  * Strips out comments from env file string
  */
-export function stripComments (envString: string): string {
+export function stripComments(envString: string): string {
   const commentsRegex = /(^#.*$)/gim
   let match = commentsRegex.exec(envString)
   let newString = envString
@@ -79,7 +95,7 @@ export function stripComments (envString: string): string {
 /**
  * Strips out newlines from env file string
  */
-export function stripEmptyLines (envString: string): string {
+export function stripEmptyLines(envString: string): string {
   const emptyLinesRegex = /(^\n)/gim
   return envString.replace(emptyLinesRegex, '')
 }
diff --git a/src/parse-rc-file.ts b/src/parse-rc-file.ts
index 3f1e036..1c0c43b 100644
--- a/src/parse-rc-file.ts
+++ b/src/parse-rc-file.ts
@@ -2,6 +2,7 @@ import { stat, readFile } from 'fs'
 import { promisify } from 'util'
 import { extname } from 'path'
 import { resolveEnvFilePath, isPromise } from './utils'
+import { Environment, RCEnvironment } from './types'
 
 const statAsync = promisify(stat)
 const readFileAsync = promisify(readFile)
@@ -9,14 +10,15 @@ const readFileAsync = promisify(readFile)
 /**
  * Gets the env vars from the rc file and rc environments
  */
-export async function getRCFileVars (
+export async function getRCFileVars(
   { environments, filePath }:
-  { environments: string[], filePath: string }
-): Promise<{ [key: string]: any }> {
+  { environments: string[], filePath: string },
+): Promise<Environment> {
   const absolutePath = resolveEnvFilePath(filePath)
   try {
     await statAsync(absolutePath)
-  } catch (e) {
+  }
+  catch {
     const pathError = new Error(`Failed to find .rc file at path: ${absolutePath}`)
     pathError.name = 'PathError'
     throw pathError
@@ -24,41 +26,45 @@ export async function getRCFileVars (
 
   // Get the file extension
   const ext = extname(absolutePath).toLowerCase()
-  let parsedData: { [key: string]: any }
+  let parsedData: Partial<RCEnvironment>
   try {
     if (ext === '.json' || ext === '.js' || ext === '.cjs') {
-      const possiblePromise = require(absolutePath) /* eslint-disable-line */
+      const possiblePromise = require(absolutePath) as PromiseLike<RCEnvironment> | RCEnvironment
       parsedData = isPromise(possiblePromise) ? await possiblePromise : possiblePromise
-    } else {
+    }
+    else {
       const file = await readFileAsync(absolutePath, { encoding: 'utf8' })
-      parsedData = JSON.parse(file)
+      parsedData = JSON.parse(file) as Partial<RCEnvironment>
     }
-  } catch (e) {
+  }
+  catch (e) {
     const errorMessage = e instanceof Error ? e.message : 'Unknown error'
     const parseError = new Error(
-      `Failed to parse .rc file at path: ${absolutePath}.\n${errorMessage}`
+      `Failed to parse .rc file at path: ${absolutePath}.\n${errorMessage}`,
     )
     parseError.name = 'ParseError'
     throw parseError
   }
 
   // Parse and merge multiple rc environments together
-  let result = {}
+  let result: Environment = {}
   let environmentFound = false
-  environments.forEach((name): void => {
-    const envVars = parsedData[name]
-    if (envVars !== undefined) {
-      environmentFound = true
-      result = {
-        ...result,
-        ...envVars
+  for (const name of environments) {
+    if (name in parsedData) {
+      const envVars = parsedData[name]
+      if (envVars != null && typeof envVars === 'object') {
+        environmentFound = true
+        result = {
+          ...result,
+          ...envVars,
+        }
       }
     }
-  })
+  }
 
   if (!environmentFound) {
     const environmentError = new Error(
-      `Failed to find environments [${environments.join(',')}] at .rc file location: ${absolutePath}`
+      `Failed to find environments [${environments.join(',')}] at .rc file location: ${absolutePath}`,
     )
     environmentError.name = 'EnvironmentError'
     throw environmentError
diff --git a/src/signal-termination.ts b/src/signal-termination.ts
index 5e4120f..73f45e4 100644
--- a/src/signal-termination.ts
+++ b/src/signal-termination.ts
@@ -1,52 +1,56 @@
 import { ChildProcess } from 'child_process'
 
 const SIGNALS_TO_HANDLE: NodeJS.Signals[] = [
-  'SIGINT', 'SIGTERM', 'SIGHUP'
+  'SIGINT', 'SIGTERM', 'SIGHUP',
 ]
 
 export class TermSignals {
-  private readonly terminateSpawnedProcessFuncHandlers: { [key: string]: any } = {}
+  private readonly terminateSpawnedProcessFuncHandlers: Record<string, NodeJS.SignalsListener> = {}
+  private terminateSpawnedProcessFuncExitHandler?: NodeJS.ExitListener
   private readonly verbose: boolean = false
   public _exitCalled = false
 
-  constructor (options: { verbose?: boolean } = {}) {
+  constructor(options: { verbose?: boolean } = {}) {
     this.verbose = options.verbose === true
   }
 
-  public handleTermSignals (proc: ChildProcess): void {
+  public handleTermSignals(proc: ChildProcess): void {
     // Terminate child process if parent process receives termination events
-    SIGNALS_TO_HANDLE.forEach((signal): void => {
-      this.terminateSpawnedProcessFuncHandlers[signal] =
-        (signal: NodeJS.Signals | number, code: number): void => {
-          this._removeProcessListeners()
-          if (!this._exitCalled) {
-            if (this.verbose) {
-              console.info(
-                'Parent process exited with signal: ' +
-                signal.toString() +
-                '. Terminating child process...')
-            }
-            // Mark shared state so we do not run into a signal/exit loop
-            this._exitCalled = true
-            // Use the signal code if it is an error code
-            let correctSignal: NodeJS.Signals | undefined
-            if (typeof signal === 'number') {
-              if (signal > (code ?? 0)) {
-                code = signal
-                correctSignal = 'SIGINT'
-              }
-            } else {
-              correctSignal = signal
-            }
-            // Kill the child process
-            proc.kill(correctSignal ?? code)
-            // Terminate the parent process
-            this._terminateProcess(code, correctSignal)
+    const terminationFunc = (signal: NodeJS.Signals | number): void => {
+      this._removeProcessListeners()
+      if (!this._exitCalled) {
+        if (this.verbose) {
+          console.info(
+            'Parent process exited with signal: '
+            + signal.toString()
+            + '. Terminating child process...')
+        }
+        // Mark shared state so we do not run into a signal/exit loop
+        this._exitCalled = true
+        // Use the signal code if it is an error code
+        // let correctSignal: NodeJS.Signals | undefined
+        if (typeof signal === 'number') {
+          if (signal > 0) {
+            // code = signal
+            signal = 'SIGINT'
           }
         }
+        // else {
+        //   correctSignal = signal
+        // }
+        // Kill the child process
+        proc.kill(signal)
+        // Terminate the parent process
+        this._terminateProcess(signal)
+      }
+    }
+
+    for (const signal of SIGNALS_TO_HANDLE) {
+      this.terminateSpawnedProcessFuncHandlers[signal] = terminationFunc
       process.once(signal, this.terminateSpawnedProcessFuncHandlers[signal])
-    })
-    process.once('exit', this.terminateSpawnedProcessFuncHandlers.SIGTERM)
+    }
+    this.terminateSpawnedProcessFuncExitHandler = terminationFunc
+    process.once('exit', this.terminateSpawnedProcessFuncExitHandler)
 
     // Terminate parent process if child process receives termination events
     proc.on('exit', (code: number | undefined, signal: NodeJS.Signals | number | null): void => {
@@ -54,9 +58,9 @@ export class TermSignals {
       if (!this._exitCalled) {
         if (this.verbose) {
           console.info(
-            `Child process exited with code: ${(code ?? '').toString()} and signal:` +
-            (signal ?? '').toString() +
-            '. Terminating parent process...'
+            `Child process exited with code: ${(code ?? '').toString()} and signal:`
+            + (signal ?? '').toString()
+            + '. Terminating parent process...',
           )
         }
         // Mark shared state so we do not run into a signal/exit loop
@@ -68,11 +72,12 @@ export class TermSignals {
             code = signal
             correctSignal = 'SIGINT'
           }
-        } else {
+        }
+        else {
           correctSignal = signal ?? undefined
         }
         // Terminate the parent process
-        this._terminateProcess(code, correctSignal)
+        this._terminateProcess(correctSignal ?? code)
       }
     })
   }
@@ -80,21 +85,25 @@ export class TermSignals {
   /**
    * Enables catching of unhandled exceptions
    */
-  public handleUncaughtExceptions (): void {
-    process.on('uncaughtException', (e): void => this._uncaughtExceptionHandler(e))
+  public handleUncaughtExceptions(): void {
+    process.on('uncaughtException', (e): void => {
+      this._uncaughtExceptionHandler(e)
+    })
   }
 
   /**
    * Terminate parent process helper
    */
-  public _terminateProcess (code?: number, signal?: NodeJS.Signals): void {
-    if (signal !== undefined) {
-      process.kill(process.pid, signal)
-      return
-    }
-    if (code !== undefined) {
-      process.exit(code)
-      return // eslint-disable-line no-unreachable
+  public _terminateProcess(signal?: NodeJS.Signals | number): void {
+    if (signal != null) {
+      if (typeof signal === 'string') {
+        process.kill(process.pid, signal)
+        return
+      }
+      if (typeof signal === 'number') {
+        process.exit(signal)
+        return
+      }
     }
     throw new Error('Unable to terminate parent process successfully')
   }
@@ -102,17 +111,19 @@ export class TermSignals {
   /**
    * Exit event listener clean up helper
    */
-  public _removeProcessListeners (): void {
+  public _removeProcessListeners(): void {
     SIGNALS_TO_HANDLE.forEach((signal): void => {
       process.removeListener(signal, this.terminateSpawnedProcessFuncHandlers[signal])
     })
-    process.removeListener('exit', this.terminateSpawnedProcessFuncHandlers.SIGTERM)
+    if (this.terminateSpawnedProcessFuncExitHandler != null) {
+      process.removeListener('exit', this.terminateSpawnedProcessFuncExitHandler)
+    }
   }
 
   /**
   * General exception handler
   */
-  public _uncaughtExceptionHandler (e: Error): void {
+  public _uncaughtExceptionHandler(e: Error): void {
     console.error(e.message)
     process.exit(1)
   }
diff --git a/src/spawn.ts b/src/spawn.ts
index 2da09b0..b4d9d5f 100644
--- a/src/spawn.ts
+++ b/src/spawn.ts
@@ -1,4 +1,4 @@
 import * as spawn from 'cross-spawn'
 export {
-  spawn
+  spawn,
 }
diff --git a/src/types.ts b/src/types.ts
index a1c1486..092c637 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,16 +1,39 @@
+import { Command } from 'commander'
+
+// Define an export type
+export type Environment = Partial<Record<string, string | number | boolean>>
+
+export type RCEnvironment = Partial<Record<string, Environment>>
+
+export interface CommanderOptions extends Command {
+  override?: boolean // Default: false
+  useShell?: boolean // Default: false
+  expandEnvs?: boolean // Default: false
+  verbose?: boolean // Default: false
+  silent?: boolean // Default: false
+  fallback?: boolean // Default false
+  environments?: string[]
+  rcFile?: string
+  file?: string
+}
+
+export interface RCFileOptions {
+  environments: string[]
+  filePath?: string
+}
+
+export interface EnvFileOptions {
+  filePath?: string
+  fallback?: boolean
+}
+
 export interface GetEnvVarOptions {
-  envFile?: {
-    filePath?: string
-    fallback?: boolean
-  }
-  rc?: {
-    environments: string[]
-    filePath?: string
-  }
+  envFile?: EnvFileOptions
+  rc?: RCFileOptions
   verbose?: boolean
 }
 
-export interface EnvCmdOptions extends Pick<GetEnvVarOptions, 'envFile' | 'rc'> {
+export interface EnvCmdOptions extends GetEnvVarOptions {
   command: string
   commandArgs: string[]
   options?: {
diff --git a/src/utils.ts b/src/utils.ts
index 12b6d3c..e5c6e50 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -4,10 +4,10 @@ import * as os from 'os'
 /**
  * A simple function for resolving the path the user entered
  */
-export function resolveEnvFilePath (userPath: string): string {
+export function resolveEnvFilePath(userPath: string): string {
   // Make sure a home directory exist
-  const home = os.homedir()
-  if (home !== undefined) {
+  const home = os.homedir() as string | undefined
+  if (home != null) {
     userPath = userPath.replace(/^~($|\/|\\)/, `${home}$1`)
   }
   return path.resolve(process.cwd(), userPath)
@@ -15,13 +15,16 @@ export function resolveEnvFilePath (userPath: string): string {
 /**
  * A simple function that parses a comma separated string into an array of strings
  */
-export function parseArgList (list: string): string[] {
+export function parseArgList(list: string): string[] {
   return list.split(',')
 }
 
 /**
- * A simple function to test if the value is a promise
+ * A simple function to test if the value is a promise/thenable
  */
-export function isPromise (value: any | PromiseLike<Object>): value is Promise<any> {
-  return value != null && typeof value.then === 'function'
+export function isPromise<T>(value?: T | PromiseLike<T>): value is PromiseLike<T> {
+  return value != null
+    && typeof value === 'object'
+    && 'then' in value
+    && typeof value.then === 'function'
 }
diff --git a/test/env-cmd.spec.ts b/test/env-cmd.spec.ts
index 2db408e..3e08264 100644
--- a/test/env-cmd.spec.ts
+++ b/test/env-cmd.spec.ts
@@ -9,9 +9,9 @@ import * as envCmdLib from '../src/env-cmd'
 
 describe('CLI', (): void => {
   let sandbox: sinon.SinonSandbox
-  let parseArgsStub: sinon.SinonStub<any, any>
-  let envCmdStub: sinon.SinonStub<any, any>
-  let processExitStub: sinon.SinonStub<any, any>
+  let parseArgsStub: sinon.SinonStub<any>
+  let envCmdStub: sinon.SinonStub<any>
+  let processExitStub: sinon.SinonStub<any>
   before((): void => {
     sandbox = sinon.createSandbox()
     parseArgsStub = sandbox.stub(parseArgsLib, 'parseArgs')
@@ -49,16 +49,16 @@ describe('CLI', (): void => {
 
 describe('EnvCmd', (): void => {
   let sandbox: sinon.SinonSandbox
-  let getEnvVarsStub: sinon.SinonStub<any, any>
-  let spawnStub: sinon.SinonStub<any, any>
-  let expandEnvsSpy: sinon.SinonSpy<any, any>
+  let getEnvVarsStub: sinon.SinonStub<any>
+  let spawnStub: sinon.SinonStub<any>
+  let expandEnvsSpy: sinon.SinonSpy<any>
   before((): void => {
     sandbox = sinon.createSandbox()
     getEnvVarsStub = sandbox.stub(getEnvVarsLib, 'getEnvVars')
     spawnStub = sandbox.stub(spawnLib, 'spawn')
     spawnStub.returns({
       on: (): void => { /* Fake the on method */ },
-      kill: (): void => { /* Fake the kill method */ }
+      kill: (): void => { /* Fake the kill method */ },
     })
     expandEnvsSpy = sandbox.spy(expandEnvsLib, 'expandEnvs')
     sandbox.stub(signalTermLib.TermSignals.prototype, 'handleTermSignals')
@@ -80,12 +80,12 @@ describe('EnvCmd', (): void => {
       commandArgs: ['-v'],
       envFile: {
         filePath: './.env',
-        fallback: true
+        fallback: true,
       },
       rc: {
         environments: ['dev'],
-        filePath: './.rc'
-      }
+        filePath: './.rc',
+      },
     })
     assert.equal(getEnvVarsStub.callCount, 1)
     assert.equal(spawnStub.callCount, 1)
@@ -100,17 +100,17 @@ describe('EnvCmd', (): void => {
         commandArgs: ['-v'],
         envFile: {
           filePath: './.env',
-          fallback: true
+          fallback: true,
         },
         rc: {
           environments: ['dev'],
-          filePath: './.rc'
-        }
+          filePath: './.rc',
+        },
       })
       assert.equal(getEnvVarsStub.callCount, 1)
       assert.equal(spawnStub.callCount, 1)
       assert.equal(spawnStub.args[0][2].env.BOB, 'test')
-    }
+    },
   )
 
   it('should not override existing env vars if noOverride option is true',
@@ -122,20 +122,20 @@ describe('EnvCmd', (): void => {
         commandArgs: ['-v'],
         envFile: {
           filePath: './.env',
-          fallback: true
+          fallback: true,
         },
         rc: {
           environments: ['dev'],
-          filePath: './.rc'
+          filePath: './.rc',
         },
         options: {
-          noOverride: true
-        }
+          noOverride: true,
+        },
       })
       assert.equal(getEnvVarsStub.callCount, 1)
       assert.equal(spawnStub.callCount, 1)
       assert.equal(spawnStub.args[0][2].env.BOB, 'cool')
-    }
+    },
   )
 
   it('should spawn process with shell option if useShell option is true',
@@ -147,20 +147,20 @@ describe('EnvCmd', (): void => {
         commandArgs: ['-v'],
         envFile: {
           filePath: './.env',
-          fallback: true
+          fallback: true,
         },
         rc: {
           environments: ['dev'],
-          filePath: './.rc'
+          filePath: './.rc',
         },
         options: {
-          useShell: true
-        }
+          useShell: true,
+        },
       })
       assert.equal(getEnvVarsStub.callCount, 1)
       assert.equal(spawnStub.callCount, 1)
       assert.equal(spawnStub.args[0][2].shell, true)
-    }
+    },
   )
 
   it('should spawn process with command and args expanded if expandEnvs option is true',
@@ -171,15 +171,15 @@ describe('EnvCmd', (): void => {
         commandArgs: ['$PING', '\\$IP'],
         envFile: {
           filePath: './.env',
-          fallback: true
+          fallback: true,
         },
         rc: {
           environments: ['dev'],
-          filePath: './.rc'
+          filePath: './.rc',
         },
         options: {
-          expandEnvs: true
-        }
+          expandEnvs: true,
+        },
       })
 
       const spawnArgs = spawnStub.args[0]
@@ -188,9 +188,9 @@ describe('EnvCmd', (): void => {
       assert.equal(spawnStub.callCount, 1)
       assert.equal(expandEnvsSpy.callCount, 3, 'command + number of args')
       assert.equal(spawnArgs[0], 'node')
-      assert.sameOrderedMembers(spawnArgs[1], ['PONG', '\\$IP'])
+      assert.sameOrderedMembers(spawnArgs[1] as string[], ['PONG', '\\$IP'])
       assert.equal(spawnArgs[2].env.PING, 'PONG')
-    }
+    },
   )
 
   it('should ignore errors if silent flag provided',
@@ -201,16 +201,16 @@ describe('EnvCmd', (): void => {
         command: 'node',
         commandArgs: ['-v'],
         envFile: {
-          filePath: './.env'
+          filePath: './.env',
         },
         options: {
-          silent: true
-        }
+          silent: true,
+        },
       })
       assert.equal(getEnvVarsStub.callCount, 1)
       assert.equal(spawnStub.callCount, 1)
       assert.isUndefined(spawnStub.args[0][2].env.BOB)
-    }
+    },
   )
 
   it('should allow errors if silent flag not provided',
@@ -221,14 +221,16 @@ describe('EnvCmd', (): void => {
           command: 'node',
           commandArgs: ['-v'],
           envFile: {
-            filePath: './.env'
-          }
+            filePath: './.env',
+          },
         })
-      } catch (e) {
+      }
+      catch (e) {
+        assert.instanceOf(e, Error)
         assert.equal(e.name, 'MissingFile')
         return
       }
       assert.fail('Should not get here.')
-    }
+    },
   )
 })
diff --git a/test/expand-envs.spec.ts b/test/expand-envs.spec.ts
index e998409..7474831 100644
--- a/test/expand-envs.spec.ts
+++ b/test/expand-envs.spec.ts
@@ -7,7 +7,9 @@ describe('expandEnvs', (): void => {
     notvar: 'this is not used',
     dollar: 'money',
     PING: 'PONG',
-    IP1: '127.0.0.1'
+    IP1: '127.0.0.1',
+    THANKSFORALLTHEFISH: 42,
+    BRINGATOWEL: true,
   }
   const args = ['notvar', '$dollar', '\\$notvar', '-4', '$PING', '$IP1', '\\$IP1', '$NONEXIST']
   const argsExpanded = ['notvar', 'money', '\\$notvar', '-4', 'PONG', '127.0.0.1', '\\$IP1', '$NONEXIST']
@@ -15,5 +17,8 @@ describe('expandEnvs', (): void => {
   it('should replace environment variables in args', (): void => {
     const res = args.map(arg => expandEnvs(arg, envs))
     assert.sameOrderedMembers(res, argsExpanded)
+    for (const arg of args) {
+      assert.typeOf(arg, 'string')
+    }
   })
 })
diff --git a/test/get-env-vars.spec.ts b/test/get-env-vars.spec.ts
index 59649b8..d1401ea 100644
--- a/test/get-env-vars.spec.ts
+++ b/test/get-env-vars.spec.ts
@@ -5,9 +5,9 @@ import * as rcFile from '../src/parse-rc-file'
 import * as envFile from '../src/parse-env-file'
 
 describe('getEnvVars', (): void => {
-  let getRCFileVarsStub: sinon.SinonStub<any, any>
-  let getEnvFileVarsStub: sinon.SinonStub<any, any>
-  let logInfoStub: sinon.SinonStub<any, any>
+  let getRCFileVarsStub: sinon.SinonStub<any>
+  let getEnvFileVarsStub: sinon.SinonStub<any>
+  let logInfoStub: sinon.SinonStub<any> | undefined
 
   before((): void => {
     getRCFileVarsStub = sinon.stub(rcFile, 'getRCFileVars')
@@ -21,9 +21,7 @@ describe('getEnvVars', (): void => {
   afterEach((): void => {
     sinon.resetHistory()
     sinon.resetBehavior()
-    if (logInfoStub !== undefined) {
-      logInfoStub.restore()
-    }
+    logInfoStub?.restore()
   })
 
   it('should parse the json .rc file from the default path with the given environment',
@@ -37,7 +35,7 @@ describe('getEnvVars', (): void => {
       assert.lengthOf(getRCFileVarsStub.args[0][0].environments, 1)
       assert.equal(getRCFileVarsStub.args[0][0].environments[0], 'production')
       assert.equal(getRCFileVarsStub.args[0][0].filePath, './.env-cmdrc')
-    }
+    },
   )
 
   it('should print path of custom .rc file and environments to info for verbose',
@@ -46,7 +44,7 @@ describe('getEnvVars', (): void => {
       getRCFileVarsStub.returns({ THANKS: 'FOR ALL THE FISH' })
       await getEnvVars({ rc: { environments: ['production'] }, verbose: true })
       assert.equal(logInfoStub.callCount, 1)
-    }
+    },
   )
 
   it('should search all default .rc file paths', async (): Promise<void> => {
@@ -71,7 +69,9 @@ describe('getEnvVars', (): void => {
     try {
       await getEnvVars({ rc: { environments: ['production'] } })
       assert.fail('should not get here.')
-    } catch (e) {
+    }
+    catch (e) {
+      assert.instanceOf(e, Error)
       assert.match(e.message, /failed to find/gi)
       assert.match(e.message, /\.rc file/gi)
       assert.match(e.message, /default paths/gi)
@@ -86,7 +86,8 @@ describe('getEnvVars', (): void => {
     try {
       await getEnvVars({ rc: { environments: ['production'] }, verbose: true })
       assert.fail('should not get here.')
-    } catch (e) {
+    }
+    catch {
       assert.equal(logInfoStub.callCount, 1)
     }
   })
@@ -98,7 +99,9 @@ describe('getEnvVars', (): void => {
     try {
       await getEnvVars({ rc: { environments: ['bad'] } })
       assert.fail('should not get here.')
-    } catch (e) {
+    }
+    catch (e) {
+      assert.instanceOf(e, Error)
       assert.match(e.message, /failed to find environments/gi)
       assert.match(e.message, /\.rc file at path/gi)
     }
@@ -112,7 +115,8 @@ describe('getEnvVars', (): void => {
     try {
       await getEnvVars({ rc: { environments: ['bad'] }, verbose: true })
       assert.fail('should not get here.')
-    } catch (e) {
+    }
+    catch {
       assert.equal(logInfoStub.callCount, 1)
     }
   })
@@ -120,7 +124,7 @@ describe('getEnvVars', (): void => {
   it('should find .rc file at custom path path', async (): Promise<void> => {
     getRCFileVarsStub.returns({ THANKS: 'FOR ALL THE FISH' })
     const envs = await getEnvVars({
-      rc: { environments: ['production'], filePath: '../.custom-rc' }
+      rc: { environments: ['production'], filePath: '../.custom-rc' },
     })
     assert.isOk(envs)
     assert.lengthOf(Object.keys(envs), 1)
@@ -136,7 +140,7 @@ describe('getEnvVars', (): void => {
     getRCFileVarsStub.returns({ THANKS: 'FOR ALL THE FISH' })
     await getEnvVars({
       rc: { environments: ['production'], filePath: '../.custom-rc' },
-      verbose: true
+      verbose: true,
     })
     assert.equal(logInfoStub.callCount, 1)
   })
@@ -147,10 +151,12 @@ describe('getEnvVars', (): void => {
     getRCFileVarsStub.rejects(pathError)
     try {
       await getEnvVars({
-        rc: { environments: ['production'], filePath: '../.custom-rc' }
+        rc: { environments: ['production'], filePath: '../.custom-rc' },
       })
       assert.fail('should not get here.')
-    } catch (e) {
+    }
+    catch (e) {
+      assert.instanceOf(e, Error)
       assert.match(e.message, /failed to find/gi)
       assert.match(e.message, /\.rc file at path/gi)
     }
@@ -164,10 +170,11 @@ describe('getEnvVars', (): void => {
     try {
       await getEnvVars({
         rc: { environments: ['production'], filePath: '../.custom-rc' },
-        verbose: true
+        verbose: true,
       })
       assert.fail('should not get here.')
-    } catch (e) {
+    }
+    catch {
       assert.equal(logInfoStub.callCount, 1)
     }
   })
@@ -178,10 +185,12 @@ describe('getEnvVars', (): void => {
     getRCFileVarsStub.rejects(environmentError)
     try {
       await getEnvVars({
-        rc: { environments: ['bad'], filePath: '../.custom-rc' }
+        rc: { environments: ['bad'], filePath: '../.custom-rc' },
       })
       assert.fail('should not get here.')
-    } catch (e) {
+    }
+    catch (e) {
+      assert.instanceOf(e, Error)
       assert.match(e.message, /failed to find environments/gi)
       assert.match(e.message, /\.rc file at path/gi)
     }
@@ -196,13 +205,14 @@ describe('getEnvVars', (): void => {
       try {
         await getEnvVars({
           rc: { environments: ['bad'], filePath: '../.custom-rc' },
-          verbose: true
+          verbose: true,
         })
         assert.fail('should not get here.')
-      } catch (e) {
+      }
+      catch {
         assert.equal(logInfoStub.callCount, 1)
       }
-    }
+    },
   )
 
   it('should parse the env file from a custom path', async (): Promise<void> => {
@@ -227,7 +237,9 @@ describe('getEnvVars', (): void => {
     try {
       await getEnvVars({ envFile: { filePath: '../.env-file' } })
       assert.fail('should not get here.')
-    } catch (e) {
+    }
+    catch (e) {
+      assert.instanceOf(e, Error)
       assert.match(e.message, /failed to find/gi)
       assert.match(e.message, /\.env file at path/gi)
     }
@@ -239,14 +251,15 @@ describe('getEnvVars', (): void => {
     try {
       await getEnvVars({ envFile: { filePath: '../.env-file' }, verbose: true })
       assert.fail('should not get here.')
-    } catch (e) {
+    }
+    catch {
       assert.equal(logInfoStub.callCount, 1)
     }
   })
 
   it(
-    'should parse the env file from the default path if custom ' +
-    'path not found and fallback option provided',
+    'should parse the env file from the default path if custom '
+    + 'path not found and fallback option provided',
     async (): Promise<void> => {
       getEnvFileVarsStub.onFirstCall().rejects('File not found.')
       getEnvFileVarsStub.returns({ THANKS: 'FOR ALL THE FISH' })
@@ -256,19 +269,19 @@ describe('getEnvVars', (): void => {
       assert.equal(envs.THANKS, 'FOR ALL THE FISH')
       assert.equal(getEnvFileVarsStub.callCount, 2)
       assert.equal(getEnvFileVarsStub.args[1][0], './.env')
-    }
+    },
   )
 
   it(
-    'should print multiple times for failure to find .env file and ' +
-    'failure to find fallback file to infor for verbose',
+    'should print multiple times for failure to find .env file and '
+    + 'failure to find fallback file to infor for verbose',
     async (): Promise<void> => {
       logInfoStub = sinon.stub(console, 'info')
       getEnvFileVarsStub.onFirstCall().rejects('File not found.')
       getEnvFileVarsStub.returns({ THANKS: 'FOR ALL THE FISH' })
       await getEnvVars({ envFile: { filePath: '../.env-file', fallback: true }, verbose: true })
       assert.equal(logInfoStub.callCount, 2)
-    }
+    },
   )
 
   it('should parse the env file from the default path', async (): Promise<void> => {
@@ -304,7 +317,9 @@ describe('getEnvVars', (): void => {
     try {
       await getEnvVars()
       assert.fail('should not get here.')
-    } catch (e) {
+    }
+    catch (e) {
+      assert.instanceOf(e, Error)
       assert.match(e.message, /failed to find/gi)
       assert.match(e.message, /\.env file/gi)
       assert.match(e.message, /default paths/gi)
@@ -319,9 +334,10 @@ describe('getEnvVars', (): void => {
       try {
         await getEnvVars({ verbose: true })
         assert.fail('should not get here.')
-      } catch (e) {
+      }
+      catch {
         assert.equal(logInfoStub.callCount, 1)
       }
-    }
+    },
   )
 })
diff --git a/test/parse-args.spec.ts b/test/parse-args.spec.ts
index b6fced0..e8443d2 100644
--- a/test/parse-args.spec.ts
+++ b/test/parse-args.spec.ts
@@ -9,7 +9,7 @@ describe('parseArgs', (): void => {
   const environments = ['development', 'production']
   const rcFilePath = './.env-cmdrc'
   const envFilePath = './.env'
-  let logInfoStub: sinon.SinonStub<any, any>
+  let logInfoStub: sinon.SinonStub<any>
 
   before((): void => {
     logInfoStub = sinon.stub(console, 'info')
@@ -53,7 +53,7 @@ describe('parseArgs', (): void => {
       assert.sameOrderedMembers(res.commandArgs, commandFlags)
       assert.notOk(res.options!.useShell)
       assert.notOk(res.envFile)
-    }
+    },
   )
 
   it('should parse override option', (): void => {
diff --git a/test/parse-env-file.spec.ts b/test/parse-env-file.spec.ts
index 0ddcdcc..22043ca 100644
--- a/test/parse-env-file.spec.ts
+++ b/test/parse-env-file.spec.ts
@@ -1,7 +1,7 @@
 import { assert } from 'chai'
 import {
   stripEmptyLines, stripComments, parseEnvVars,
-  parseEnvString, getEnvFileVars
+  parseEnvString, getEnvFileVars,
 } from '../src/parse-env-file'
 
 describe('stripEmptyLines', (): void => {
@@ -20,10 +20,12 @@ describe('stripComments', (): void => {
 
 describe('parseEnvVars', (): void => {
   it('should parse out all env vars in string when not ending with \'\\n\'', (): void => {
-    const envVars = parseEnvVars('BOB=COOL\nNODE_ENV=dev\nANSWER=42 AND COUNTING')
+    const envVars = parseEnvVars('BOB=COOL\nNODE_ENV=dev\nANSWER=42 AND COUNTING\nNUMBER=42\nBOOLEAN=true')
     assert(envVars.BOB === 'COOL')
     assert(envVars.NODE_ENV === 'dev')
     assert(envVars.ANSWER === '42 AND COUNTING')
+    assert(envVars.NUMBER === 42)
+    assert(envVars.BOOLEAN === true)
   })
 
   it('should parse out all env vars in string with format \'key=value\'', (): void => {
@@ -96,7 +98,7 @@ describe('parseEnvString', (): void => {
     const env = parseEnvString('BOB=COOL\nNODE_ENV=dev\nANSWER=42\n')
     assert(env.BOB === 'COOL')
     assert(env.NODE_ENV === 'dev')
-    assert(env.ANSWER === '42')
+    assert(env.ANSWER === 42)
   })
 })
 
@@ -107,7 +109,8 @@ describe('getEnvFileVars', (): void => {
       THANKS: 'FOR WHAT?!',
       ANSWER: 42,
       ONLY: 'IN PRODUCTION',
-      GALAXY: 'hitch\nhiking'
+      GALAXY: 'hitch\nhiking',
+      BRINGATOWEL: true,
     })
   })
 
@@ -117,7 +120,8 @@ describe('getEnvFileVars', (): void => {
       THANKS: 'FOR WHAT?!',
       ANSWER: 42,
       ONLY: 'IN\n PRODUCTION',
-      GALAXY: 'hitch\nhiking\n\n'
+      GALAXY: 'hitch\nhiking\n\n',
+      BRINGATOWEL: true,
     })
   })
 
@@ -126,7 +130,7 @@ describe('getEnvFileVars', (): void => {
     assert.deepEqual(env, {
       THANKS: 'FOR ALL THE FISH',
       ANSWER: 0,
-      GALAXY: 'hitch\nhiking'
+      GALAXY: 'hitch\nhiking',
     })
   })
 
@@ -134,7 +138,7 @@ describe('getEnvFileVars', (): void => {
     const env = await getEnvFileVars('./test/test-files/test-async.js')
     assert.deepEqual(env, {
       THANKS: 'FOR ALL THE FISH',
-      ANSWER: 0
+      ANSWER: 0,
     })
   })
 
@@ -142,9 +146,10 @@ describe('getEnvFileVars', (): void => {
     const env = await getEnvFileVars('./test/test-files/test')
     assert.deepEqual(env, {
       THANKS: 'FOR WHAT?!',
-      ANSWER: '42',
+      ANSWER: 42,
       ONLY: 'IN=PRODUCTION',
-      GALAXY: 'hitch\nhiking'
+      GALAXY: 'hitch\nhiking',
+      BRINGATOWEL: true,
     })
   })
 
@@ -152,7 +157,9 @@ describe('getEnvFileVars', (): void => {
     try {
       await getEnvFileVars('./test/test-files/non-existent-file')
       assert.fail('Should not get here!')
-    } catch (e) {
+    }
+    catch (e) {
+      assert.instanceOf(e, Error)
       assert.match(e.message, /file path/gi)
     }
   })
diff --git a/test/parse-rc-file.spec.ts b/test/parse-rc-file.spec.ts
index 2b74213..1f61a12 100644
--- a/test/parse-rc-file.spec.ts
+++ b/test/parse-rc-file.spec.ts
@@ -11,7 +11,8 @@ describe('getRCFileVars', (): void => {
     assert.deepEqual(res, {
       THANKS: 'FOR WHAT?!',
       ANSWER: 42,
-      ONLY: 'IN PRODUCTION'
+      ONLY: 'IN PRODUCTION',
+      BRINGATOWEL: true,
     })
   })
 
@@ -20,7 +21,7 @@ describe('getRCFileVars', (): void => {
     assert.exists(res)
     assert.deepEqual(res, {
       THANKS: 'FOR MORE FISHIES',
-      ANSWER: 21
+      ANSWER: 21,
     })
   })
 
@@ -28,7 +29,9 @@ describe('getRCFileVars', (): void => {
     try {
       await getRCFileVars({ environments: ['bad'], filePath: 'bad-path' })
       assert.fail('Should not get here!')
-    } catch (e) {
+    }
+    catch (e) {
+      assert.instanceOf(e, Error)
       assert.match(e.message, /\.rc file at path/gi)
     }
   })
@@ -37,7 +40,9 @@ describe('getRCFileVars', (): void => {
     try {
       await getRCFileVars({ environments: ['bad'], filePath: rcFilePath })
       assert.fail('Should not get here!')
-    } catch (e) {
+    }
+    catch (e) {
+      assert.instanceOf(e, Error)
       assert.match(e.message, /environments/gi)
     }
   })
@@ -46,7 +51,9 @@ describe('getRCFileVars', (): void => {
     try {
       await getRCFileVars({ environments: ['bad'], filePath: './test/test-files/.rc-test-bad-format' })
       assert.fail('Should not get here!')
-    } catch (e) {
+    }
+    catch (e) {
+      assert.instanceOf(e, Error)
       assert.match(e.message, /parse/gi)
     }
   })
@@ -54,12 +61,13 @@ describe('getRCFileVars', (): void => {
   it('should parse an async js .rc file', async (): Promise<void> => {
     const env = await getRCFileVars({
       environments: ['production'],
-      filePath: './test/test-files/.rc-test-async.js'
+      filePath: './test/test-files/.rc-test-async.js',
     })
     assert.deepEqual(env, {
       THANKS: 'FOR WHAT?!',
       ANSWER: 42,
-      ONLY: 'IN PRODUCTION'
+      ONLY: 'IN PRODUCTION',
+      BRINGATOWEL: true,
     })
   })
 })
diff --git a/test/signal-termination.spec.ts b/test/signal-termination.spec.ts
index 96ad89c..4657eed 100644
--- a/test/signal-termination.spec.ts
+++ b/test/signal-termination.spec.ts
@@ -1,6 +1,9 @@
 import { assert } from 'chai'
 import * as sinon from 'sinon'
 import { TermSignals } from '../src/signal-termination'
+import { ChildProcess } from 'child_process'
+
+type ChildExitListener = (code: number | null, signal: NodeJS.Signals | null | number) => void
 
 describe('signal-termination', (): void => {
   let sandbox: sinon.SinonSandbox
@@ -15,8 +18,8 @@ describe('signal-termination', (): void => {
   describe('TermSignals', (): void => {
     describe('_uncaughtExceptionHandler', (): void => {
       const term = new TermSignals()
-      let logStub: sinon.SinonStub<any, any>
-      let processStub: sinon.SinonStub<any, any>
+      let logStub: sinon.SinonStub<any>
+      let processStub: sinon.SinonStub<any>
 
       beforeEach((): void => {
         logStub = sandbox.stub(console, 'error')
@@ -39,7 +42,7 @@ describe('signal-termination', (): void => {
 
     describe('_removeProcessListeners', (): void => {
       const term = new TermSignals()
-      let removeListenerStub: sinon.SinonStub<any, any>
+      let removeListenerStub: sinon.SinonStub<any>
       before((): void => {
         removeListenerStub = sandbox.stub(process, 'removeListener')
       })
@@ -50,15 +53,15 @@ describe('signal-termination', (): void => {
 
       it('should remove all listeners from default signals and exit signal', (): void => {
         term._removeProcessListeners()
-        assert.equal(removeListenerStub.callCount, 4)
-        assert.equal(removeListenerStub.args[3][0], 'exit')
+        assert.equal(removeListenerStub.callCount, 3)
+        assert.oneOf(removeListenerStub.args[2][0], ['SIGTERM', 'SIGINT', 'SIGHUP'])
       })
     })
 
     describe('_terminateProcess', (): void => {
       const term = new TermSignals()
-      let exitStub: sinon.SinonStub<any, any>
-      let killStub: sinon.SinonStub<any, any>
+      let exitStub: sinon.SinonStub<any>
+      let killStub: sinon.SinonStub<any>
 
       beforeEach((): void => {
         exitStub = sandbox.stub(process, 'exit')
@@ -83,7 +86,7 @@ describe('signal-termination', (): void => {
       })
 
       it('should call kill method with correct kill signal', (): void => {
-        term._terminateProcess(1, 'SIGINT')
+        term._terminateProcess('SIGINT')
         assert.equal(killStub.callCount, 1)
         assert.equal(exitStub.callCount, 0)
         assert.equal(killStub.args[0][1], 'SIGINT')
@@ -93,7 +96,9 @@ describe('signal-termination', (): void => {
         try {
           term._terminateProcess()
           assert.fail('should not get here')
-        } catch (e) {
+        }
+        catch (e) {
+          assert.instanceOf(e, Error)
           assert.match(e.message, /unable to terminate parent process/gi)
         }
       })
@@ -101,8 +106,8 @@ describe('signal-termination', (): void => {
 
     describe('handleUncaughtExceptions', (): void => {
       const term = new TermSignals()
-      let processOnStub: sinon.SinonStub<any, any>
-      let _uncaughtExceptionHandlerStub: sinon.SinonStub<any, any>
+      let processOnStub: sinon.SinonStub<any>
+      let _uncaughtExceptionHandlerStub: sinon.SinonStub<any>
 
       before((): void => {
         processOnStub = sandbox.stub(process, 'on')
@@ -117,22 +122,22 @@ describe('signal-termination', (): void => {
         term.handleUncaughtExceptions()
         assert.equal(processOnStub.callCount, 1)
         assert.equal(_uncaughtExceptionHandlerStub.callCount, 0)
-        processOnStub.args[0][1]()
+        ;(processOnStub.args[0][1] as () => void)()
         assert.equal(_uncaughtExceptionHandlerStub.callCount, 1)
       })
     })
 
     describe('handleTermSignals', (): void => {
       let term: TermSignals
-      let procKillStub: sinon.SinonStub<any, any>
-      let procOnStub: sinon.SinonStub<any, any>
-      let processOnceStub: sinon.SinonStub<any, any>
-      let _removeProcessListenersStub: sinon.SinonStub<any, any>
-      let _terminateProcessStub: sinon.SinonStub<any, any>
-      let logInfoStub: sinon.SinonStub<any, any>
-      let proc: any
-
-      function setup (verbose: boolean = false): void {
+      let procKillStub: sinon.SinonStub<any>
+      let procOnStub: sinon.SinonStub<any>
+      let processOnceStub: sinon.SinonStub<any>
+      let _removeProcessListenersStub: sinon.SinonStub<any>
+      let _terminateProcessStub: sinon.SinonStub<any>
+      let logInfoStub: sinon.SinonStub<any>
+      let proc: ChildProcess
+
+      function setup(verbose = false): void {
         term = new TermSignals({ verbose })
         procKillStub = sandbox.stub()
         procOnStub = sandbox.stub()
@@ -141,8 +146,8 @@ describe('signal-termination', (): void => {
         _terminateProcessStub = sandbox.stub(term, '_terminateProcess')
         proc = {
           kill: procKillStub,
-          on: procOnStub
-        }
+          on: procOnStub,
+        } as unknown as ChildProcess
       }
 
       beforeEach((): void => {
@@ -163,7 +168,7 @@ describe('signal-termination', (): void => {
       it('should terminate child process if parent process terminated', (): void => {
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        processOnceStub.args[0][1]('SIGTERM', 1)
+        ;(processOnceStub.args[0][1] as NodeJS.SignalsListener)('SIGTERM')
         assert.equal(_removeProcessListenersStub.callCount, 1)
         assert.equal(procKillStub.callCount, 1)
         assert.equal(_terminateProcessStub.callCount, 1)
@@ -176,17 +181,17 @@ describe('signal-termination', (): void => {
         logInfoStub = sandbox.stub(console, 'info')
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        processOnceStub.args[0][1]('SIGTERM', 1)
+        ;(processOnceStub.args[0][1] as NodeJS.SignalsListener)('SIGTERM')
         assert.equal(logInfoStub.callCount, 1)
       })
 
-      it('should not terminate child process if child process termination ' +
-        'has already been called by parent', (): void => {
+      it('should not terminate child process if child process termination '
+        + 'has already been called by parent', (): void => {
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        processOnceStub.args[0][1]('SIGINT', 1)
+        ;(processOnceStub.args[0][1] as NodeJS.SignalsListener)('SIGINT')
         assert.isOk(term._exitCalled)
-        processOnceStub.args[0][1]('SIGTERM', 1)
+        ;(processOnceStub.args[0][1] as NodeJS.SignalsListener)('SIGTERM')
         assert.equal(_removeProcessListenersStub.callCount, 2)
         assert.equal(procKillStub.callCount, 1)
         assert.equal(_terminateProcessStub.callCount, 1)
@@ -196,7 +201,7 @@ describe('signal-termination', (): void => {
       it('should convert and use number signal as code', (): void => {
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        processOnceStub.args[0][1](4, 1)
+        ;(processOnceStub.args[0][1] as NodeJS.ExitListener)(1)
         assert.equal(_removeProcessListenersStub.callCount, 1)
         assert.equal(procKillStub.callCount, 1)
         assert.equal(procKillStub.args[0][0], 'SIGINT')
@@ -204,13 +209,13 @@ describe('signal-termination', (): void => {
         assert.isOk(term._exitCalled)
       })
 
-      it('should not use signal number as code if value is 0', (): void => {
+      it('should not use default signal if code is 0', (): void => {
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        processOnceStub.args[0][1](0, 1)
+        ;(processOnceStub.args[0][1] as NodeJS.ExitListener)(0)
         assert.equal(_removeProcessListenersStub.callCount, 1)
         assert.equal(procKillStub.callCount, 1)
-        assert.equal(procKillStub.args[0], 1)
+        assert.equal(procKillStub.args[0], 0)
         assert.equal(_terminateProcessStub.callCount, 1)
         assert.isOk(term._exitCalled)
       })
@@ -218,7 +223,7 @@ describe('signal-termination', (): void => {
       it('should use signal value and default SIGINT signal if code is undefined', (): void => {
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        processOnceStub.args[0][1](4, undefined)
+        ;(processOnceStub.args[0][1] as NodeJS.ExitListener)(4)
         assert.equal(_removeProcessListenersStub.callCount, 1)
         assert.equal(procKillStub.callCount, 1)
         assert.equal(procKillStub.args[0][0], 'SIGINT')
@@ -229,7 +234,7 @@ describe('signal-termination', (): void => {
       it('should terminate parent process if child process terminated', (): void => {
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        procOnStub.args[0][1](1, 'SIGTERM')
+        ;(procOnStub.args[0][1] as ChildExitListener)(1, 'SIGTERM')
         assert.equal(_removeProcessListenersStub.callCount, 1)
         assert.equal(_terminateProcessStub.callCount, 1)
         assert.isOk(term._exitCalled)
@@ -241,31 +246,31 @@ describe('signal-termination', (): void => {
         logInfoStub = sandbox.stub(console, 'info')
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        procOnStub.args[0][1](1, 'SIGTERM')
+        ;(procOnStub.args[0][1] as ChildExitListener)(1, 'SIGTERM')
         assert.equal(logInfoStub.callCount, 1)
       })
 
       it(
-        'should print parent process terminated to info for verbose when ' +
-        'code and signal are undefined',
+        'should print parent process terminated to info for verbose when '
+        + 'code and signal are undefined',
         (): void => {
           sandbox.restore()
           setup(true)
           logInfoStub = sandbox.stub(console, 'info')
           assert.notOk(term._exitCalled)
           term.handleTermSignals(proc)
-          procOnStub.args[0][1](undefined, null)
+          ;(procOnStub.args[0][1] as ChildExitListener)(null, null)
           assert.equal(logInfoStub.callCount, 1)
-        }
+        },
       )
 
       it('should not terminate parent process if parent process already terminating', (): void => {
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        procOnStub.args[0][1](1, 'SIGINT')
+        ;(procOnStub.args[0][1] as ChildExitListener)(1, 'SIGINT')
         assert.equal(_removeProcessListenersStub.callCount, 1)
         assert.equal(_terminateProcessStub.callCount, 1)
-        procOnStub.args[0][1](1, 'SIGTERM')
+        ;(procOnStub.args[0][1] as ChildExitListener)(1, 'SIGTERM')
         assert.equal(_removeProcessListenersStub.callCount, 2)
         assert.equal(_terminateProcessStub.callCount, 1)
         assert.isOk(term._exitCalled)
@@ -274,7 +279,7 @@ describe('signal-termination', (): void => {
       it('should convert null signal value to undefined', (): void => {
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        procOnStub.args[0][1](0, null)
+        ;(procOnStub.args[0][1] as ChildExitListener)(0, null)
         assert.equal(_removeProcessListenersStub.callCount, 1)
         assert.equal(_terminateProcessStub.callCount, 1)
         assert.strictEqual(_terminateProcessStub.firstCall.args[1], undefined)
@@ -284,33 +289,30 @@ describe('signal-termination', (): void => {
       it('should convert and use number signal as code', (): void => {
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        procOnStub.args[0][1](1, 4)
+        ;(procOnStub.args[0][1] as ChildExitListener)(1, 4)
         assert.equal(_removeProcessListenersStub.callCount, 1)
         assert.equal(_terminateProcessStub.callCount, 1)
-        assert.strictEqual(_terminateProcessStub.firstCall.args[0], 4)
-        assert.strictEqual(_terminateProcessStub.firstCall.args[1], 'SIGINT')
+        assert.strictEqual(_terminateProcessStub.firstCall.args[0], 'SIGINT')
         assert.isOk(term._exitCalled)
       })
 
       it('should not use signal number as code if value is 0', (): void => {
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        procOnStub.args[0][1](1, 0)
+        ;(procOnStub.args[0][1] as ChildExitListener)(1, 0)
         assert.equal(_removeProcessListenersStub.callCount, 1)
         assert.equal(_terminateProcessStub.callCount, 1)
         assert.strictEqual(_terminateProcessStub.firstCall.args[0], 1)
-        assert.isUndefined(_terminateProcessStub.firstCall.args[1])
         assert.isOk(term._exitCalled)
       })
 
       it('should use signal value and default SIGINT signal if code is undefined', (): void => {
         assert.notOk(term._exitCalled)
         term.handleTermSignals(proc)
-        procOnStub.args[0][1](null, 1)
+        ;(procOnStub.args[0][1] as ChildExitListener)(null, 1)
         assert.equal(_removeProcessListenersStub.callCount, 1)
         assert.equal(_terminateProcessStub.callCount, 1)
-        assert.strictEqual(_terminateProcessStub.firstCall.args[0], 1)
-        assert.strictEqual(_terminateProcessStub.firstCall.args[1], 'SIGINT')
+        assert.strictEqual(_terminateProcessStub.firstCall.args[0], 'SIGINT')
         assert.isOk(term._exitCalled)
       })
     })
diff --git a/test/test-files/.rc-test b/test/test-files/.rc-test
index 57aea54..d76f2e2 100644
--- a/test/test-files/.rc-test
+++ b/test/test-files/.rc-test
@@ -10,6 +10,7 @@
   "production": {
     "THANKS": "FOR WHAT?!",
     "ANSWER": 42,
-    "ONLY": "IN PRODUCTION"
+    "ONLY": "IN PRODUCTION",
+    "BRINGATOWEL": true
   }
-}
\ No newline at end of file
+}
diff --git a/test/test-files/.rc-test-async.js b/test/test-files/.rc-test-async.js
index a3fb453..356914f 100644
--- a/test/test-files/.rc-test-async.js
+++ b/test/test-files/.rc-test-async.js
@@ -1,19 +1,20 @@
 module.exports = new Promise((resolve) => {
   setTimeout(() => {
     resolve({
-      'development': {
-        'THANKS': 'FOR ALL THE FISH',
-        'ANSWER': 0
+      development: {
+        THANKS: 'FOR ALL THE FISH',
+        ANSWER: 0,
       },
-      'test': {
-        'THANKS': 'FOR MORE FISHIES',
-        'ANSWER': 21
+      test: {
+        THANKS: 'FOR MORE FISHIES',
+        ANSWER: 21,
+      },
+      production: {
+        THANKS: 'FOR WHAT?!',
+        ANSWER: 42,
+        ONLY: 'IN PRODUCTION',
+        BRINGATOWEL: true,
       },
-      'production': {
-        'THANKS': 'FOR WHAT?!',
-        'ANSWER': 42,
-        'ONLY': 'IN PRODUCTION'
-      }
     })
   }, 200)
 })
diff --git a/test/test-files/.rc-test.json b/test/test-files/.rc-test.json
index 57aea54..d76f2e2 100644
--- a/test/test-files/.rc-test.json
+++ b/test/test-files/.rc-test.json
@@ -10,6 +10,7 @@
   "production": {
     "THANKS": "FOR WHAT?!",
     "ANSWER": 42,
-    "ONLY": "IN PRODUCTION"
+    "ONLY": "IN PRODUCTION",
+    "BRINGATOWEL": true
   }
-}
\ No newline at end of file
+}
diff --git a/test/test-files/test b/test/test-files/test
index bee4cae..bd9a1d2 100644
--- a/test/test-files/test
+++ b/test/test-files/test
@@ -1,4 +1,5 @@
 THANKS = FOR WHAT?!
 ANSWER=42
 ONLY= "IN=PRODUCTION"
-GALAXY="hitch\nhiking"
\ No newline at end of file
+GALAXY="hitch\nhiking"
+BRINGATOWEL=true
diff --git a/test/test-files/test-async.js b/test/test-files/test-async.js
index ba95d4d..7ba707d 100644
--- a/test/test-files/test-async.js
+++ b/test/test-files/test-async.js
@@ -2,7 +2,7 @@ module.exports = new Promise((resolve) => {
   setTimeout(() => {
     resolve({
       THANKS: 'FOR ALL THE FISH',
-      ANSWER: 0
+      ANSWER: 0,
     })
   }, 200)
 })
diff --git a/test/test-files/test-newlines.json b/test/test-files/test-newlines.json
index 912f322..52d404b 100644
--- a/test/test-files/test-newlines.json
+++ b/test/test-files/test-newlines.json
@@ -2,5 +2,6 @@
   "THANKS": "FOR WHAT?!",
   "ANSWER": 42,
   "ONLY": "IN\n PRODUCTION",
-  "GALAXY": "hitch\nhiking\n\n" 
-}
\ No newline at end of file
+  "GALAXY": "hitch\nhiking\n\n",
+  "BRINGATOWEL": true
+}
diff --git a/test/test-files/test.js b/test/test-files/test.js
index 0ef99e6..5e25974 100644
--- a/test/test-files/test.js
+++ b/test/test-files/test.js
@@ -1,5 +1,5 @@
 module.exports = {
   THANKS: 'FOR ALL THE FISH',
   ANSWER: 0,
-  GALAXY: 'hitch\nhiking'
+  GALAXY: 'hitch\nhiking',
 }
diff --git a/test/test-files/test.json b/test/test-files/test.json
index a90c062..379f9c6 100644
--- a/test/test-files/test.json
+++ b/test/test-files/test.json
@@ -2,5 +2,6 @@
   "THANKS": "FOR WHAT?!",
   "ANSWER": 42,
   "ONLY": "IN PRODUCTION",
-  "GALAXY": "hitch\nhiking" 
-}
\ No newline at end of file
+  "GALAXY": "hitch\nhiking",
+  "BRINGATOWEL": true
+}
diff --git a/test/utils.spec.ts b/test/utils.spec.ts
index 479ad3d..8afac0e 100644
--- a/test/utils.spec.ts
+++ b/test/utils.spec.ts
@@ -48,5 +48,13 @@ describe('utils', (): void => {
       const res = isPromise({})
       assert.isFalse(res)
     })
+    it('should return false for string', (): void => {
+      const res = isPromise('test')
+      assert.isFalse(res)
+    })
+    it('should return false for undefined', (): void => {
+      const res = isPromise(undefined)
+      assert.isFalse(res)
+    })
   })
 })
diff --git a/tsconfig.eslint.json b/tsconfig.eslint.json
deleted file mode 100644
index 17ae7bb..0000000
--- a/tsconfig.eslint.json
+++ /dev/null
@@ -1,12 +0,0 @@
-{
-  "extends": "./tsconfig.json",
-  "compilerOptions": {
-    "allowJs": true,
-    "checkJs": true
-  },
-  "include": [
-    "src/**/*",
-    "test/**/*",
-    "bin/**/*"
-  ]
-}
\ No newline at end of file