Prerequisites

• [x ] Checked that your issue isn't already filed by cross referencing issues with the common mistake label
• Checked next-gen ES issues and syntax problems by using the same environment and/or transpiler configuration without Mocha to ensure it isn't just a feature that actually isn't supported in the environment in question or a bug in your code.
• [ x] 'Smoke tested' the code to be tested by running it outside the real test suite to get a better sense of whether the problem is in the code under test, your usage of Mocha, or Mocha itself
• [ x] Ensured that there is no discrepancy between the locally and globally installed versions of Mocha. You can find them with:
  node node_modules/.bin/mocha --version(Local) and mocha --version(Global). We recommend avoiding the use of globally installed Mocha.

Description

I have been running specific set of tests for few years now and have been always upgrading to the latest mocha and everything was ok.
With mocha 4 suddenly all tests are passing but it doesn't end as if the --no-exit is automatically added although I never added it.

Steps to Reproduce

Expected behavior:
After all tests end, the process should stop even if there are timeoutes or sockets that prevent the process from existing.

Actual behavior:
Mocha 4 process waits forever like mocha 3 with --no-exit flag

Reproduces how often:
With our tests always. I have 700 tests so it is hard to pinpoint which one casuses the issue or if maybe it is in our codebase.

Versions

mocha 4.0.0 fails. before that everything works good.