Simplify mongodb example by using preset

CHANGELOG.md

@@ -14,6 +14,7 @@
 ### Chore & Maintenance
 
 - `[expect]` Fix label and add opposite assertion for toEqual tests ([#8288](https://github.com/facebook/jest/pull/8288))
+- `[docs]` Mention Jest MongoDB Preset ([#8318](https://github.com/facebook/jest/pull/8318))
 
 ### Performance
 

docs/MongoDB.md

@@ -5,142 +5,57 @@ title: Using with MongoDB
 
 With the [Global Setup/Teardown](Configuration.md#globalsetup-string) and [Async Test Environment](Configuration.md#testenvironment-string) APIs, Jest can work smoothly with [MongoDB](https://www.mongodb.com/).
 
-## A jest-mongodb example
+## Use jest-mongodb Preset
 
-The basic idea is to:
+[Jest MongoDB](https://github.com/shelfio/jest-mongodb) provides all required configuration to run your tests using MongoDB.
 
-1.  Spin up in-memory mongodb server
-2.  Export a global variable with mongo URI
-3.  Write tests for queries / aggregations using a real database ✨
-4.  Shut down mongodb server using Global Teardown
+1.  First install `@shelf/jest-mongodb`
 
-Here's an example of the GlobalSetup script
-
-```js
-// setup.js
-const path = require('path');
-
-const fs = require('fs');
-
-const {MongoMemoryServer} = require('mongodb-memory-server');
-
-const globalConfigPath = path.join(__dirname, 'globalConfig.json');
-
-const mongod = new MongoMemoryServer({
-  autoStart: false,
-});
-
-module.exports = async () => {
-  if (!mongod.isRunning) {
-    await mongod.start();
-  }
-
-  const mongoConfig = {
-    mongoDBName: 'jest',
-    mongoUri: await mongod.getConnectionString(),
-  };
-
-  // Write global config to disk because all tests run in different contexts.
-  fs.writeFileSync(globalConfigPath, JSON.stringify(mongoConfig));
-
-  // Set reference to mongod in order to close the server during teardown.
-  global.__MONGOD__ = mongod;
-};
+```
+yarn add @shelf/jest-mongodb --dev
 ```
 
-Then we need a custom Test Environment for Mongo
-
-```js
-// mongo-environment.js
-const NodeEnvironment = require('jest-environment-node');
-
-const path = require('path');
-
-const fs = require('fs');
-
-const globalConfigPath = path.join(__dirname, 'globalConfig.json');
-
-class MongoEnvironment extends NodeEnvironment {
-  constructor(config) {
-    super(config);
-  }
-
-  async setup() {
-    console.log('Setup MongoDB Test Environment');
-
-    const globalConfig = JSON.parse(fs.readFileSync(globalConfigPath, 'utf-8'));
-
-    this.global.__MONGO_URI__ = globalConfig.mongoUri;
-    this.global.__MONGO_DB_NAME__ = globalConfig.mongoDBName;
-
-    await super.setup();
-  }
-
-  async teardown() {
-    console.log('Teardown MongoDB Test Environment');
-
-    await super.teardown();
-  }
+2.  Specify preset in your Jest configuration:
 
-  runScript(script) {
-    return super.runScript(script);
-  }
+```json
+{
+  "preset": "@shelf/jest-mongodb"
 }
-
-module.exports = MongoEnvironment;
 ```
 
-Finally we can shut down mongodb server
+3.  Write your test
 
 ```js
-// teardown.js
-module.exports = async function() {
-  await global.__MONGOD__.stop();
-};
-```
+const {MongoClient} = require('mongodb');
 
-With all the things set up, we can now write our tests like this:
+describe('insert', () => {
+  let connection;
+  let db;
 
-```js
-// test.js
-const {MongoClient} = require('mongodb');
+  beforeAll(async () => {
+    connection = await MongoClient.connect(global.__MONGO_URI__, {
+      useNewUrlParser: true,
+    });
+    db = await connection.db(global.__MONGO_DB_NAME__);
+  });
 
-let connection;
-let db;
+  afterAll(async () => {
+    await connection.close();
+    await db.close();
+  });
 
-beforeAll(async () => {
-  connection = await MongoClient.connect(global.__MONGO_URI__);
-  db = await connection.db(global.__MONGO_DB_NAME__);
-});
+  it('should insert a doc into collection', async () => {
+    const users = db.collection('users');
 
-afterAll(async () => {
-  await connection.close();
-  await db.close();
-});
+    const mockUser = {_id: 'some-user-id', name: 'John'};
+    await users.insertOne(mockUser);
 
-it('should aggregate docs from collection', async () => {
-  const files = db.collection('files');
-
-  await files.insertMany([
-    {type: 'Document'},
-    {type: 'Video'},
-    {type: 'Image'},
-    {type: 'Document'},
-    {type: 'Image'},
-    {type: 'Document'},
-  ]);
-
-  const topFiles = await files
-    .aggregate([
-      {$group: {_id: '$type', count: {$sum: 1}}},
-      {$sort: {count: -1}},
-    ])
-    .toArray();
-
-  expect(topFiles).toEqual([
-    {_id: 'Document', count: 3},
-    {_id: 'Image', count: 2},
-    {_id: 'Video', count: 1},
-  ]);
+    const insertedUser = await users.findOne({_id: 'some-user-id'});
+    expect(insertedUser).toEqual(mockUser);
+  });
 });
 ```
+
+There's no need to load any dependencies.
+
+See [documentation](https://github.com/shelfio/jest-mongodb) for details (configuring MongoDB version, etc).