MongoDB In-Memory Server

const mongod = new MongoMemoryServer({
  instance?: {
    port?: number, // by default choose any free port
    ip?: string, // by default '127.0.0.1', for binding to all IP addresses set it to `::,0.0.0.0`,
    dbName?: string, // by default '' (empty string)
    dbPath?: string, // by default create in temp directory
    storageEngine?: string, // by default `ephemeralForTest`(unless mongodb 7.0.0, where its `wiredTiger`), available engines: [ 'ephemeralForTest', 'wiredTiger' ]
    replSet?: string, // by default no replica set, replica set name
    args?: string[], // by default no additional arguments, any additional command line arguments for `mongod` `mongod` (ex. ['--notablescan'])
    auth?: boolean, // add "--auth" argument, dont use this directly use top-level "auth"
  },
  binary?: {
    version?: string, // by default '7.0.14'
    downloadDir?: string, // see the documentation on what is chosen by default https://typegoose.github.io/mongodb-memory-server/docs/api/config-options#download_dir
    platform?: string, // by default os.platform()
    arch?: string, // by default os.arch()
    checkMD5?: boolean, // by default false OR process.env.MONGOMS_MD5_CHECK
    systemBinary?: string, // by default undefined or process.env.MONGOMS_SYSTEM_BINARY
  },
  // using "auth" will manage "instance.auth"
  auth?: {
    // enable needs to be set to "true", otherwise automatic user creation is by default disabled
    enable?: boolean, // enable automatic user creation
    customRootName?: string, // by default "mongodb-memory-server-root"
    customRootPwd?: string, // by default "rootuser"
    force?: boolean, // force creation of users
    keyfileContent?: string, // by default "0123456789" (only useful for replsets)
    extraUsers?: [{
      // see mongodb documentation https://docs.mongodb.com/manual/reference/method/db.createUser/#definition)
      createUser: string, // user name
      pwd: string, // user password
      roles: UserRoles[], // user roles
      database?: string, // which database the user is created on
      customData?: Record<string, any>, // any arbitrary information, see mongodb documentation
      mechanisms?: ('SCRAM-SHA-1' | 'SCRAM-SHA-256')[],
      authenticationRestrictions?: {
        clientSource?: string;
        serverAddress?: string;
      }[],
      digestPassword?: boolean,
    }],
  },
});

const replSet = new MongoMemoryReplSet({
  binary: binaryOpts, // same as for MongoMemoryServer
  instanceOpts: [
    {
      args, // any additional instance specific args
      port, // port number for the instance
      dbPath, // path to database files for this instance
      storageEngine, // same storage engine options
    },
    // each entry will result in a MongoMemoryServer (replSet.count will not limit the amount spawned by "instanceOpts")
  ],
  // unless otherwise noted below these values will be in common with all instances spawned:
  replSet: {
    name, // replica set name (default: 'testset')
    auth?: boolean | AutomaticAuth, // enable auth, for options see #available-options-for-mongomemoryserver
    args, // any args specified here will be combined with any per instance args from `instanceOpts`
    count, // number of additional `mongod` processes to start (will not start any extra if instanceOpts.length > replSet.count); (default: 1)
    dbName, // default database for db URI strings
    ip, // by default '127.0.0.1', for binding to all IP addresses set it to `::,0.0.0.0`
    spawn, // spawn options when creating the child processes
    storageEngine, // default storage engine for instance. (Can be overridden per instance)
    configSettings: {
      // Optional settings for 'replSetInitiate' command. See https://docs.mongodb.com/manual/reference/command/replSetInitiate/
      chainingAllowed: boolean, // When true it allows secondary members to replicate from other secondary members. When false, secondaries can replicate only from the primary.
      heartbeatTimeoutSecs: number, // Number of seconds that the replica set members wait for a successful heartbeat from each other. If a member does not respond in time, other members mark the delinquent member as inaccessible.
      heartbeatIntervalMillis: number, // The frequency in milliseconds of the heartbeats.
      electionTimeoutMillis: number, // The time limit in milliseconds for detecting when a replica set’s primary is unreachable.
      catchUpTimeoutMillis: number, // Time limit for a newly elected primary to sync (catch up) with the other replica set members that may have more recent writes.
    },
  },
});

// assuming mongoose@6.x
import mongoose from 'mongoose';
import { MongoMemoryServer } from 'mongodb-memory-server';

const mongoServer = await MongoMemoryServer.create();

(async () => {
  await mongoose.connect(mongoServer.getUri(), { dbName: "verifyMASTER" });

  // your code here
  
  await mongoose.disconnect();
})();