What you are describing is the normal behavior for Mocha. This code illustrates what happens if you do not try to trap exceptions in asynchronous code (even raised by assertion failures) and what you can do if you want to avoid the uncaught exception message:

var assert = require(assert);



it(fails with uncaught exception, function (done) {

    setTimeout(function () {

        assert.equal(1, 2);

        done();

    }, 1000);

});



it(fails with assertion error, function (done) {

    setTimeout(function () {

        try {

            assert.equal(1, 2);

            done();

        }

        catch (e) {

            done(e);

        }

    }, 1000);

});

The code above produces this output:

  1) fails

  2) fails



  0 passing (2s)

  2 failing



  1)  fails:

     Uncaught AssertionError: 1 == 2

      at null._onTimeout (/tmp/t2/test.js:5:16)

      at Timer.listOnTimeout [as ontimeout] (timers.js:112:15)



  2)  fails:

     AssertionError: 1 == 2

      at null._onTimeout (/tmp/t2/test.js:13:20)

      at Timer.listOnTimeout [as ontimeout] (timers.js:112:15)