Unit Testing

Choosing Sociable or Solitary Unit Tests

Choosing Sociable or Solitary Unit Tests A unit test fails after a harmless refactor. The production behaviour is still correct, but the test expected an internal collaborator to receive exactly three calls. Elsewhere, a different unit test passes even though two real classes no longer work together, because both sides were replaced with mocks. Both tests are isolated in some sense, yet they give poor feedback for different reasons. The useful question isn’t simply whether unit tests should use mocks. It is where the test boundary should be.