If you are using Karma and the test fails, and you might want to debug the unit test step by step. This is pretty easy to do. I will show how to do this using my library of lazy assertions called lazy-ass . All tests pass when running them once $ karma start karma.conf.js --browsers=Chrome INFO [karma]: Karma v0.12.16 server started at http://localhost:9876/ INFO [launcher]: Starting browser Chrom