如何编写用于使用mongoose，mocha和chai将对象插入和检索到mongodb的单元测试？

Question

I'm trying to write a unit test for inserting (and then retrieving) a document to mongodb. However, I keep getting a timeout error, and it suggests that done is never called. (Mongod is running, and I can see the objects being inserted just fine as well as being retrieved, using console.log.)

What I'm using:

Node.js, ES6, Mongoose, Mocha, Chai

CheckbookEntry is a weird wrapper to some Mongoose calls that let's me work with promises.

    describe('create and getOneById', () => {
    it('creates a new checkbookEntry, and retrieves it from the db', (done) => {
        var EXAMPLE_ENTRY = {
            type: 'debit',
            date: Date(),
            description: 'Example of a cb entry',
            account: 'PNC',
            amount: 239.33
        };

        CheckbookEntry.create(EXAMPLE_ENTRY.type,
                              EXAMPLE_ENTRY.date,
                              EXAMPLE_ENTRY.description,
                              EXAMPLE_ENTRY.account,
                              EXAMPLE_ENTRY.amount)
                        .then(function(createdEntry){
                            return CheckbookEntry.getOneById(createdEntry._id);
                        })
                        .then(function(foundEntry){
                            expect(foundEntry).to.eql(EXAMPLE_ENTRY);
                            done();
                        }, function(err){
                            assert.fail(err);
                            done();
                        });
    }).timeout(5000);

}); // end describe create

Any suggestions on how to get this working?

Answer 1

I can only guess, but I think that the problem may be caused by this:

.then(function(foundEntry){
    expect(foundEntry).to.eql(EXAMPLE_ENTRY);
    done();
}, function(err){
    assert.fail(err);
    done();
});

More specifically, using assertions in a fulfilled/rejection handler without continuing the promise chain.

If the assertion throws an exception, done() will never get called. And depending on which promise implementation is being used, you might never even get notified about the exception. Also, an exception thrown in the onFulFilled handler won't trigger the onRejected handler passed to the same .then() method.

Because Mocha supports promises out of the box , instead of using the done callback, return your promise chain:

return CheckbookEntry.create(...)
                     .then(...)
                     .then(..., ...);

That way, the exception will get propagated back to Mocha, which will handle it.

FWIW, Mongoose also supports promises out of the box .