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Signs That Your Unit Tests Are Not Helpful

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Here are two metrics that you can look at with your unit tests:
Percentage of test failures that are only a problem with the unit test, not a problem with the code running in a real environment. This often happens when you are mocking interfaces.Percentage of times that a bug fix or otherwise non breaking change requires an update to a unit test.The goal would be to have both these percentages at 0%. This would indicate that every test failure represents a real issue in your code and that only feature changes require updates to the unit tests. As these percentages approach 100% the less helpful your unit tests become. However what percentage should act as the cut for when your unit tests are a net positive verse when they are a net negative? We can make two assumptions:
Every test failure that reflects a real code issue exactly out weighs every false positive.Every unit test update that comes from a non feature change is out weighed by the benefits of having a unit test that comes from…