test-db-setup.js

const mongoose = require("mongoose");
mongoose.set("useCreateIndex", true);
mongoose.promise = global.Promise;

async function removeAllCollections() {
	const collections = Object.keys(mongoose.connection.collections);
	for (const collectionName of collections) {
		const collection = mongoose.connection.collections[collectionName];
		await collection.deleteMany();
	}
}

async function dropAllCollections() {
	const collections = Object.keys(mongoose.connection.collections);
	for (const collectionName of collections) {
		const collection = mongoose.connection.collections[collectionName];
		try {
			await collection.drop();
		} catch (error) {
			// Sometimes this error happens, but you can safely ignore it
			if (error.message === "ns not found") return;
			// This error occurs when you use it.todo. You can
			// safely ignore this error too
			if (error.message.includes("a background operation is currently running"))
				return;
			console.log(error.message);
		}
	}
}

module.exports = {
	setupDB(databaseName) {
		// Connect to Mongoose
		beforeAll(async () => {
			const url = process.env.DB_URL ?? `mongodb://127.0.0.1/${databaseName}`;
			await mongoose.connect(url, {
				useNewUrlParser: true,
				useUnifiedTopology: true,
				useCreateIndex: true,
			});
		});

		// Clear collections after each test
		afterEach(() => {
			return removeAllCollections();
		});

		// Disconnect Mongoose
		afterAll(async () => {
			await dropAllCollections();
			await mongoose.connection.close();
		});
	},
	removeAllCollections,
};