Agreed. When you mock, you're essentially writing your implementation twice. Once for the real implementation, and again via the mock interactions. Sometimes, t

Agreed. When you mock, you're essentially writing your implementation twice. Once for the real implementation, and again via the mock interactions. Sometimes, this type of test is helpful in the way that you can catch typos by writing the same piece of prose twice. However, these tests quickly become burdensome to maintain, e.g. changing an implementation in a way that produces identical results requires updating tests even though the behavior is unchanged.