Sinon stub.resolves() not acting as desired - node.js

Question

Here's the function I'm writing tests for:
ensureUserDoesNotExist(request, response, next) {
this.User.findOne({ where: { email: request.body.email }})
.then(user => {
if (user) {
response.sendStatus(403);
} else {
next();
}
});
}
And here's the test that I cannot get to pass:
it('should return a 403 if a matching user is found', () => {
mockRequest.body.email = 'test#email.com';
userController.User.findOne.resolves(true); // This is a previously created sinon stub
userController.ensureUserDoesNotExist(mockRequest, mockResponse, mockNext);
assert(mockResponse.sendStatus.calledWith(403));
});
It fails, simply claiming that the stub isn't called (at all, for what it's worth).
I strongly suspect this is to do with the promise - or Sinon's interaction with it - but am having a complete mind-blank in trying to figure out exactly what. The code works as intended (or it did when I last looked before playing about with it). Can anyone help me out?

Answer 1

Your assertion is evaluated before the end request
You need to return the promise
ensureUserDoesNotExist(request, response, next) {
return this.User.findOne({ where: { email: request.body.email }})
.then(user => {
if (user) {
response.sendStatus(403);
} else {
next();
}
});
}
and assert in then clause
it('should return a 403 if a matching user is found', () => {
mockRequest.body.email = 'test#email.com';
userController.User.findOne.resolves(true); // This is a previously created sinon stub
userController.ensureUserDoesNotExist(mockRequest, mockResponse, mockNext).then(() => {
assert(mockResponse.sendStatus.calledWith(403));
});
});

Answer 2

The test also must return a promise to indicate an asynchronous test to Mocha. You can use the one returned by the then call:
it('should return a 403 if a matching user is found', () => {
mockRequest.body.email = 'test#email.com';
userController.User.findOne.resolves(true); // This is a previously created sinon stub
return userController.ensureUserDoesNotExist(mockRequest, mockResponse, mockNext).then(() => {
assert(mockResponse.sendStatus.calledWith(403));
});
});