I've been having several issues with Karma which are very difficult to debug. Some of them are the result of errors in my code, or errors in library code. Sometimes it's very difficult to track down which tests are causing it to fail.
EDIT: The tests are hanging, then timing out with no error. The coverage report ends up saying that I have 100% coverage.
One thing that has helped is to go through each test and add describe.only( instead of describe. That allows me to narrow down the problematic tests. This is an awful way to debug. Is there any way to have Karma print to the console the test suite it is currently running?