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@shelf/jest-mongodb

repository·master·Indexed 20 days ago

https://github.com/shelfio/jest-mongodb

A Jest preset that runs a MongoDB memory server for testing, allowing integration tests against a real, isolated MongoDB instance. It provides a custom TestEnvironment (MongoEnvironment) to automate the lifecycle of the server and injects connection details via global variables like __MONGO_URI__ and __MONGO_DB_NAME__. Supports shared or separate databases for Jest workers and replica set configurations via jest-mongodb-config.js.

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What's inside @shelf/jest-mongodb

  3. Configure Jest with @shelf/jest-mongodb preset

    master

    Create a jest.config.js file and set the preset property to @shelf/jest-mongodb.

    Important: If you are using a custom jest.config.js, ensure you remove the testEnvironment property, as it will conflict with the preset.

    module.exports = {
  preset: '@shelf/jest-mongodb',
};

  5. How the MongoEnvironment manages the MongoDB lifecycle

    master

    The MongoEnvironment class (exported as module.exports) is a custom Jest TestEnvironment that automates the lifecycle of a MongoDB instance for your tests.

    Lifecycle Stages:

    1. Initialization: During construction, it reads configuration from globalConfig.json (located in the Jest root directory) to determine whether to start a MongoMemoryServer or a MongoMemoryReplSet.
    2. Setup: When tests run, the environment starts the MongoDB instance (if a mongoUri is not already provided in the global config) and injects two key global variables into the test context:
      • global.__MONGO_URI__: The connection string for the running MongoDB instance.
      • global.__MONGO_DB_NAME__: The name of the database to use (defaults to a random UUID if not specified in globalConfig.json).
    3. Teardown: When tests finish, the environment automatically stops the MongoDB instance to clean up resources.

  6. Avoid infinite loops in Jest watch mode

    master

    The package creates a globalConfig.json file in the project root. When running Jest with the --watch flag, changes to this file can trigger an infinite loop. To prevent this, add globalConfig to your watchPathIgnorePatterns in jest.config.js.

    // jest.config.js
module.exports = {
  watchPathIgnorePatterns: ['globalConfig'],
};

  7. Use separate databases for each Jest worker

    master

    To ensure each Jest worker uses its own separate database, set useSharedDBForAllJestWorkers: false in jest-mongodb-config.js. Note that when using this option, the process.env variable is not created.

    module.exports = {
  mongodbMemoryServerOptions: {
    binary: {
      skipMD5: true,
    },
    autoStart: false,
    instance: {},
  },

  useSharedDBForAllJestWorkers: false,
};

  8. Configure custom MongoDB URI environment variable name

    master

    By default, the library uses process.env.MONGO_URL. To use a different environment variable name, set the mongoURLEnvName field in jest-mongodb-config.js.

    module.exports = {
  mongodbMemoryServerOptions: {
    binary: {
      version: '4.0.3',
      skipMD5: true,
    },
    instance: {},
    autoStart: false,
  },
  mongoURLEnvName: 'MONGODB_URI',
};

  9. Use a shared database for all Jest workers

    master

    To use the same database instance across all Jest workers, specify a dbName within the instance object in jest-mongodb-config.js.

    module.exports = {
  mongodbMemoryServerOptions: {
    binary: {
      version: '4.0.3',
      skipMD5: true,
    },
    instance: {
      dbName: 'jest',
    },
    autoStart: false,
  },
};

  10. Configure MongoDB as a Replica Set

    master

    To run MongoDB as a replica set, add a replSet object to mongodbMemoryServerOptions and specify the count and storageEngine fields.

    module.exports = {
  mongodbMemoryServerOptions: {
    binary: {
      skipMD5: true,
    },
    autoStart: false,
    instance: {},
    replSet: {
      count: 3,
      storageEngine: 'wiredTiger',
    },
  },
};

  11. Connect to MongoDB in tests using global.__MONGO_URI__

    master

    While the library sets process.env.MONGO_URL, it is preferable to use global.__MONGO_URI__ when connecting your MongoClient. This ensures compatibility when useSharedDBForAllJestWorkers: false is configured.

    const {MongoClient} = require('mongodb');

describe('insert', () => {
  let connection;
  let db;

  beforeAll(async () => {
    connection = await MongoClient.connect(global.__MONGO_URI__, {});
    db = await connection.db();
  });

  afterAll(async () => {
    await connection.close();
  });
});

  12. Configure jest-mongodb via the Config interface

    master

    The Config interface defines the options available for setting up the jest-mongodb environment. This configuration is typically used to control how the in-memory server is instantiated and how workers interact with the database.

    Available configuration keys:

    • mongodbMemoryServerOptions: Options passed directly to mongodb-memory-server (supports both MongoMemoryReplSetOpts and MongoMemoryServerOpts).
    • mongoURLEnvName: The name of the environment variable that will hold the MongoDB URI. Defaults to 'MONGO_URL'.
    • useSharedDBForAllJestWorkers: Determines if all Jest workers should share the same database instance. Defaults to true.
    export interface Config {
  mongodbMemoryServerOptions?: MongoMemoryReplSetOpts | MongoMemoryServerOpts;
  /**
   * @default 'MONGO_URL'
   */
  mongoURLEnvName?: string;
  /**
   * @default true
   */
  useSharedDBForAllJestWorkers?: boolean;
}