"When you get assigned a bug to fix, what's the first thing you do?"
Difference between unit and integration testing
Each is meant to provide a different benefit than the other, but the fact that integration testing can be used for less effective unit testing leads to confusion of where the boundaries should lie.
Unit test behavior, not implementation
I think it’s fantastic that we’re starting to write unit tests, but the hardest part about writing unit tests in knowing what to test. As a succinct message, I like “Test behavior, not implementation.”