Strange behavior when comparing objects for equality

[emirotin]

Here's a sample repo https://github.com/emirotin/mocha-async-fail
There are 4 skipped tests, all built around testing objects equality (there's also 1 running test to demonstrate that there're not configuration errors).

All tests has 2 nested async calls with done() called from the inner.
Both tests use mongo-pool2 package which simply creates MongoDB connection and opens it (thus you need local mongo running on default port, or adjust the settings in the beginning of the file).

Now I "un-skip" tests 1 by 1 and see these results:

The test should not be ok - 1 compares 2 "plain" objects {} for equality inside of the 1st callback. This test properly fails, lists the failing test and shows the diff

Uncaught AssertionError: expected {} to be {}
                                         + expected - actual

This proves that mocha properly handles async exceptions.

The test should not be ok - 2 does the same, but inside the 2nd callback. Same proper result.
This proves that callbacks depth is not the problem per se.

The test should not be ok - 3 compares db connection object to "plain" object {} inside of the 1st callback. This test fails, test suite exits, but does not report which test failed:

  ․․․․

  1 passing (86ms)
  2 pending
  1 failing

  (end of output)

Finally, the test should not be ok - 4 compares two db objects inside of the 2nd callback. This test fails as well, but the suite never exits.

If it matters:
OS X 10.9
node version 0.10.26
mocha version 1.17.1
shouldjs version 3.1.3

[mrjoelkemp]

Agreed. This is pretty strange. I managed to get your tests to work (fail and exit) by doing a console.log at the following locations marked with // LOGGING:

  it('should not be ok - 3', function (done) {
    mongoPool.connect(config, function(err, db1) {
      (!err).should.be.ok;
      (!!db1).should.be.ok;
      console.log('bar') // LOGGING
      // tests exit, but without error erporting
      (db1).should.be.equal({});
      mongoPool.connect(config, function(err, db2) {
        (!err).should.be.ok;
        (!!db2).should.be.ok;
        (db1).should.be.equal({});
        done();
      }, false);
    });
  });

  it('should not be ok - 4', function (done) {
    mongoPool.connect(config, function(err, db1) {
      (!err).should.be.ok;
      (!!db1).should.be.ok;
      mongoPool.connect(config, function(err, db2) {
        (!err).should.be.ok;
        console.log('foo') // LOGGING
        (!!db2).should.be.ok;
        // tests do not exit at all
        (db1).should.be.equal({});
        done();
      }, false);
    });
  });

It'll take me a bit longer to debug through this.

[mrjoelkemp]

The cases below should be equivalent to your tests (without the use of mongo2-pool). These cases work as expected: failing and exiting. This leads me to believe that the problem is caused by mongo2-pool and not Mocha. Unless I'm missing something, I'd say this is a 'wontfix'.

  it('should not be ok - 3', function (done) {
    var db1 = {},
        err = null,
        db2 = {};

    setImmediate(function () {
      (!err).should.be.ok;
      (!!db1).should.be.ok;
      // tests exit, but without error erporting
      (db1).should.be.equal({});
      setImmediate(function () {
        (!err).should.be.ok;
        (!!db2).should.be.ok;
        (db1).should.be.equal({});
        done();
      });
    });
  });

  it('should not be ok - 4', function (done) {
    var db1 = {},
        err = null,
        db2 = {};

    setImmediate(function () {
      (!err).should.be.ok;
      (!!db1).should.be.ok;
      setImmediate(function () {
        (!err).should.be.ok;
        console.log('foo')
        (!!db2).should.be.ok;
        // tests do not exit at all
        (db1).should.be.equal({});
        done();
      });
    });
  });

[emirotin]

Yes, this is not reproducible with simpler objects.
My guess was it may be related to deeply comparing too big objects, or may be because they have some circular references.

I think this is mocha issue, a here's why:

• mongo-pool2 does not do anything extraordinary on its own and is battle-tested in production
• even if mongo-pool2 is doing something wrong, it does not explain inconsistent behavior of mocha. I mean I just ask it to compare 2 objects of some nature, they are either equal or not, right? But it shows us 4 different behaviors.

[mrjoelkemp]

My guess was it may be related to deeply comparing too big objects, or may be because they have some circular references.

Probably related to #1140.

[boneskull]

please re-open if still issue