My Vue Library Had 99% Line Coverage. Mutation Testing Found Two Bugs Anyway.
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On October 2nd, vue-smart-loading-kit had 1,369 unit tests and 99% line coverage. That afternoon I added Stryker for mutation testing. About an hour and a half later I released 0.3.1 with fixes for two bugs my tests had missed. What mutation testing checks Coverage tells you which lines ran during your tests. It can't tell you whether a test would fail if one of those lines were wrong. Stryker checks that part. It makes one small change to your source at a time, like flipping a cond