Unit tests use karma + Mocha (in TDD mode) + and Firefox Nightly.

• Write tests that are resistant to flux in the codebase. Things move quickly.
• When testing with an <a-entity>, we often to have wait until it fires the 'loaded' event.
• karma may misreport test failures to other unit tests. Run one test suite at a time to isolate the test failure.
• Use process.nextTick after doing DOM manipulations. May have to use setTimeout when doing removeAttribute.
• Use suite.only or test.only to isolate test cases.