That’s the seductive power of mocking - you get a test up and running quickly. The benefit to the initial test writer is significant.
The cost is the pain - sometimes nightmarish - for other contributors to the code base since tests depending on mocking are far more brittle.
Someone changes code to check if the ResultSet is empty before further processing and a large number of your mock based tests break as the original test author will only have mocked enough of the class to support the current implementation.
Working on a 10+ year old code base, making a small simple safe change and then seeing a bunch of unit tests fail, my reaction is always “please let the failing tests not rely on mocks”.
The cost is the pain - sometimes nightmarish - for other contributors to the code base since tests depending on mocking are far more brittle.
Someone changes code to check if the ResultSet is empty before further processing and a large number of your mock based tests break as the original test author will only have mocked enough of the class to support the current implementation.
Working on a 10+ year old code base, making a small simple safe change and then seeing a bunch of unit tests fail, my reaction is always “please let the failing tests not rely on mocks”.