My posts : https://www.56kode.com/
Your tests either catch real issues — or they don't.
It’s not something to run on every push.
But from time to time? It’s eye-opening 👀
Your tests either catch real issues — or they don't.
It’s not something to run on every push.
But from time to time? It’s eye-opening 👀
🧹 When cleaning up a legacy project
🧠 When improving test quality
🚨 When you think your code is well tested — but want proof
🧹 When cleaning up a legacy project
🧠 When improving test quality
🚨 When you think your code is well tested — but want proof
Mutation testing is slow.
🔁 It can multiply test time by 10x or more
🧱 It may require config tweaks to work with your test setup
🐢 In CI, it can make feedback loops way longer
Mutation testing is slow.
🔁 It can multiply test time by 10x or more
🧱 It may require config tweaks to work with your test setup
🐢 In CI, it can make feedback loops way longer
✅ It doesn’t just check if your code is covered
✅ It checks if your tests are actually useful
And that’s a huge difference.
✅ It doesn’t just check if your code is covered
✅ It checks if your tests are actually useful
And that’s a huge difference.
return a > b;
Mutation testing might change it to:
return a < b;
If your tests still pass... do they really check the logic? 🤔
return a > b;
Mutation testing might change it to:
return a < b;
If your tests still pass... do they really check the logic? 🤔
- The tool (like Stryker) changes your code on purpose
- It runs your test suite
- If tests fail → good!
- If tests pass → bad sign: the mutation slipped through
- The tool (like Stryker) changes your code on purpose
- It runs your test suite
- If tests fail → good!
- If tests pass → bad sign: the mutation slipped through