Step 4.3: Add chat field to Query type

schema/resolvers.ts

@@ -21,6 +21,10 @@ const resolvers = {
     chats() {
       return chats;
     },
+
+    chat(root: any, { chatId }: any) {
+      return chats.find(c => c.id === chatId);
+    },
   },
 };
 

schema/typeDefs.graphql

@@ -17,4 +17,5 @@ type Chat {
 
 type Query {
   chats: [Chat!]!
+  chat(chatId: ID!): Chat
 }

tests/queries/__snapshots__/getChat.test.ts.snap

@@ -0,0 +1,16 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Query.chat should fetch specified chat 1`] = `
+Object {
+  "chat": Object {
+    "id": "1",
+    "lastMessage": Object {
+      "content": "You on your way?",
+      "createdAt": "2018-12-31T07:20:00.000Z",
+      "id": "1",
+    },
+    "name": "Ethan Gonzalez",
+    "picture": "https://randomuser.me/api/portraits/thumb/men/1.jpg",
+  },
+}
+`;

tests/queries/getChat.test.ts

@@ -0,0 +1,33 @@
+import { createTestClient } from 'apollo-server-testing';
+import { ApolloServer, gql } from 'apollo-server-express';
+import schema from '../../schema';
+
+describe('Query.chat', () => {
+  it('should fetch specified chat', async () => {
+    const server = new ApolloServer({ schema });
+
+    const { query } = createTestClient(server);
+
+    const res = await query({
+      variables: { chatId: '1' },
+      query: gql`
+        query GetChat($chatId: ID!) {
+          chat(chatId: $chatId) {
+            id
+            name
+            picture
+            lastMessage {
+              id
+              content
+              createdAt
+            }
+          }
+        }
+      `,
+    });
+
+    expect(res.data).toBeDefined();
+    expect(res.errors).toBeUndefined();
+    expect(res.data).toMatchSnapshot();
+  });
+});

types/apollo-server-testing.d.ts

@@ -0,0 +1,27 @@
+declare module 'apollo-server-testing' {
+  import { ApolloServerBase } from 'apollo-server-core';
+  import { print, DocumentNode } from 'graphql';
+  import { GraphQLResponse } from 'graphql-extensions';
+
+  type StringOrAst = string | DocumentNode;
+
+  // A query must not come with a mutation (and vice versa).
+  type Query<TVariables> = {
+    query: StringOrAst;
+    mutation?: undefined;
+    variables?: TVariables;
+  };
+
+  type Mutation<TVariables> = {
+    mutation: StringOrAst;
+    query?: undefined;
+    variables?: TVariables;
+  };
+
+  export const createTestClient: <TVariables>(
+    server: ApolloServerBase
+  ) => {
+    query: (query: Query<TVariables>) => Promise<GraphQLResponse>;
+    mutate: (mutation: Mutation<TVariables>) => Promise<GraphQLResponse>;
+  };
+}