mocha wait for db connection before running tests - node.js

Question

Basically to run the tests, I need the database connection to MongoDb to be ready. The database manager has a connect method to get a connection and a get method to get a reference to that connection. The connect method is supposed to be called only once, at startup. This design works fine when running the app because the app starts only if the connect method has been called and returned a connection.
The database manager using mongo native (no mongoskin, no mongoose) (database.js):
var config = require('../config')
var MongoClient = require('mongodb').MongoClient
var connection = null
module.exports.connect = function () {
return MongoClient.connect(config.mongodb.uri + config.mongodb.db)
.then(function (db) {
connection = db
})
}
module.exports.get = function () {
if (!connection) {
throw new Error('Call connect first!')
}
return connection
}
Start the app:
var db = require('./services/database');
db.connect()
.then(function() {
logger.info("mongodb is running");
require('./main')
});
In the application, there are service modules and repository modules. The service modules require repository modules when they have to use the database. I have a BaseRepository module where I define the common queries findOne, findAll, etc. For all the MongoDb collections I have a specific repository that inherits from the BaseRepository. In the constructor, I set the collection by calling the database connection.
It means that when a service module which has a dependency on a repository module, the database connect method has to be called. This is the issue because I don't know how to start all the tests after the call to that connect method. I am open to suggestions if you think it's a design flow.
A test:
var usersService = require('../../services/rest/UsersService');
describe('IT Test', function () {
})
The service:
var usersRepository = require('../dao/UsersRepository');
The repository:
var db = require('../database');
var BaseRepository = require('./BaseRepository');
var util = require('util');
util.inherits(UsersRepository, BaseRepository);
function UsersRepository() {
this.collection = db.get().collection('users'); // <====== The connect method has not been called yet
}
The base repository:
function BaseRepository() {
this.collection = undefined;
}
BaseRepository.prototype.findOne = function (filters) {
return this.collection.findOne(filters)
}

Answer 1

I ended up writing a wrapper for all the tests
'use strict'
var logger = require('../services/logger')()
var db = require('../services/database')
describe('All tests wrapper', function () {
it('should pass', function () {
return db.connect()
.then(function () {
logger.info('MongoDB is running')
require('./agenda/AgendaJobsIT')
require('./dashboard/DashboardsServiceIT')
require('./twitter/TwitterServiceTest')
require('./authentication/TokenServiceTest')
})
})
})

Answer 2

The best way is mocha --delayed switch. mocha doc says
If you need to perform asynchronous operations before any of your suites are run (e.g., for dynamically generating tests), you may delay the root suite. Run mocha with the --delay flag.
For example, use mocha in this way mocha --recursive --exit --delay --ui tdd tests.js and --delayed enable you to trigger running the root suite via calling run() explicitly.
const fn = async x => {
return new Promise(resolve => {
setTimeout(resolve, 1500, 2 * x);
});
};
(async function() {
const z = await fn(3);
suite("won't run until run() executes", () => {})
run();
})();
For more information, please read https://mochajs.org/#delayed-root-suite.