I am new to Mocha + Chai. I wrote a few simple tests that calls my app routes and validates the responses and it works great for endpoints that do not have dependencies to other APIs or to a database.

Now I am struggling trying to find a way to test a route I have that internally ends up calling a database. I can’t actually call the database so I am look for a way to mock it. I am reading on sinon but I fail to understand if what I need is possible with it, and how.

My tests are like:

it('should return 200 when data is valid', function (done) {
chai
  .request(app)
  .post('/my/endpoint')
  .accept('application/json')
  .type('json')
  .send({
    data: '1234'
  })
  .end(function (err, res) {
    res.should.have.status(200);
    //other assertions
    done();
  });

});

The “/my/endpoint” calls a service that then calls a mongo database.
Is there a simple way to mock the db call?
I already extracted the database client instance to a separate file in hopes I could easily mock it.