High test coverage is not the same as good test coverage. A suite with 90% coverage can still let critical bugs through if the tests are brittle or testing the wrong things.

The Testing Pyramid Still Matters

Unit tests are cheap to write and fast to run. Integration tests verify that components work together. End-to-end tests confirm the user journey works. The pyramid means lots of unit tests, fewer E2E tests — not because E2E tests are bad, but because suites dominated by them are slow and fragile.

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A flaky test is worse than no test. It trains your team to ignore failures — and that is when real bugs slip through.

Integrating Tests into CI

Tests only prevent bugs if they run on every change. Configure your CI pipeline to run the full suite on every pull request and block merges on failure. Keep the feedback loop under 10 minutes.