There is what I consider to be an important caveat near the end: In essence classic xunit tests are not just unit tests, but also mini-integration tests. As a

There is what I consider to be an important caveat near the end: In essence classic xunit tests are not just unit tests, but also mini-integration tests. As a result many people like the fact that client tests may catch errors that the main tests for an object may have missed, particularly probing areas where classes interact. Mockist tests lose that quality. In addition you also run the risk that expectations on mockist tests can be incorrect, resulting in unit tests that run green but mask inherent errors.