Node: 7.2.1
Mocha: 3.2.0
MacOSX: Sierra (10.12.3)
Cmdline: mocha my_test.js

Seeing mocha exit with a 0 exit code after failing a test in an after each hook. I traced it down to this code:

The function is called with the correct exit code, but then stream.write('', done); doesn't call the callback before the process terminates.