alt Hacker News> 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.
So this change doesn't allow an empty result set, something that is no longer allowed by the new implementation but was allowed previously. Isn't that the sort of breaking change you want your regression tests to catch?
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akoboldfrying • today at 3:30 AM
It doesn't have to be a breaking change -- an empty result set could still be allowed. It could simply be a perf improvement that avoids calling an expensive function with an empty result set, when it is known that the function is a no-op in this case.
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I used ResultSet because the comment above mentioned it. A clearer example of what I’m talking about might be say you replace “x.size() > 0” with “!x.isEmpty()” when x is a mocked instance of class X.
If tests (authored by someone else) break, I now have to figure out whether the breakage is due to the fact that not enough behavior was mocked or whether I have inadvertently broken something. Maybe it’s actually important that code avoid using “isEmpty”? Or do I just mock the isEmpty call and hope for the best? What if the existing mocked behavior for size() is non-trivial?
Typically you’re not dealing with something as obvious.