Can mutating the code under test make a stable test go flaky? Yes, and it happens more than you think!

Introduction What if changing the code under test — not the test itself and not the execution environment — could turn a perfectly stable test case into a flaky one? That is exactly what my colleagues and I discovered in a new phenomenon that we call “test flimsiness”. The name is an acronym since FLIM siness stands for FL akiness I nduced by M utations to the code under test. In (Parry et al.…