Mocha/Chai tests hanging at .should.be.deep.equal despite result existing - node.js

Question

I'm running some tests using Mocha and chai. One of the tests is hanging at a .should.be.deep.equal call.
Here's the test code:
// Make the fake connection before running tests
before(function(done) {
mongoose.connect('mongodb://fake.test/TestingDB', function(err) {
done(err);
});
});
// Test Cases
describe('Testing the functions that deal with users and locations:', function() {
// Test Setup
var req = {};
beforeEach(function(done) {
mockgoose.reset()
async.parallel([function(callback){
sensors.create(testData.deviceData, function(err, model) {
if (err) {console.log(err)}
callback();
});
}, function(callback) {
locations.create(testData.locationData, function(err, model) {
if (err) {console.log(err)}
callback();
});
}], function(err) {
done();
});
});
afterEach(function(done) {
mockgoose.reset();
done();
});
// Tests
describe('function locationList', function() {
it('should list the test location', function(done) {
dbFunctions.locationList(req, function(result) {
console.log(result) //Prints the whole result
console.log(testData.locationList)
result.should.exist; //This doesn't cause it to hang
result.should.be.deep.equal(testData.locationList) //hangs here
done(result);
});
})
})
});
And here's the function it's testing:
exports.locationList = function(req, callback) {
listLocations().then(
function(data) {
callback(data);
},
function(err) {
console.log('Error Retrieving Location Information: ' + err);
callback(err);
});
};
As I note in the comments, the results object exists and gets printed to the console. results.should.exist; doesn't throw an exception and if I comment out everything but it the test works fine. For some weird reason, despite both the testData.locationList and result object existing, the test times out. I have 14 other tests that use the exact same syntax without any problems. Does anyone know what could be causing this to happen for this specific test?
Here's the output from the tests:
Testing the functions that deal with users and locations:
function locationList
[ { devices: {},
address: '123 Fake St, Waterloo, On',
location: 'Unittest',
owner: 'unit#test.com',
_id: '-1' } ]
[ { devices: {},
address: '123 Fake St, Waterloo, On',
location: 'Unittest',
owner: 'unit#test.com',
_id: '-1' } ]
1) should list the test location
0 passing (2s)
1 failing
1) Testing the functions that deal with users and locations: function locationList should list the test location:
Error: timeout of 2000ms exceeded. Ensure the done() callback is being called in this test.
at null.<anonymous> (C:\Users\My Name\AppData\Roaming\npm\node_modules\mocha\lib\runnable.js:189:19)
Extending the timeout doesn't work. Nor does putting something random (ie. the integer 1 in the .should.be.deep.equal() function.

Answer 1

My guess is that the callback in exports.locationList is called synchronously, and that your test case is actually failing, throwing an exception, which never gets caught because the callback is (synchronously) called from within a promise handler (more info here).
Try and see if this works better:
dbFunctions.locationList(req, function(result) {
setImmediate(function() {
console.log(result) //Prints the whole result
console.log(testData.locationList)
result.should.exist; //This doesn't cause it to hang
result.should.be.deep.equal(testData.locationList) //hangs here
done(result);
});
});
// or use a module like dezalgo (https://github.com/npm/dezalgo)
The underlying cause may be mockgoose.
Also, you're not using the proper Node.js conventions where the first argument to a callback function is "reserved" for errors. In other words, your code should look similar to this:
if (err) {
callback(err);
} else {
callback(null, data);
}
You're now passing both errors and data as the first argument.

Answer 2

A guess: Maybe the issue lies with mongoose decorating the result with it's own functions/members, and one of them somehow getting stuck in an infinite loop when chai tries to enumerate them all to perform a deep comparison.