Testing Strategies That Actually Stick
Most testing advice focuses on what to test. The harder problem is building a testing culture that survives deadlines, new engineers, and the inevitable 'we'll add tests later' spiral.
By The Weekly Dev —
The coverage trap
A team I worked with had 94% test coverage and a broken deploy pipeline. The tests passed. The product didn't work. Coverage is a proxy metric, and proxies fail when optimized for directly.
What tests are actually for
Tests are documentation that runs. The best tests describe what a system does in language that any engineer can read and verify. A test suite is a spec.
This reframe changes what you write. Instead of "does this function return the right value for these inputs," the question becomes "does this behavior match what we promised to users."
The three tests worth writing
Unit tests for pure functions with non-obvious logic. Parsing, calculations, transformations. Fast, isolated, high confidence per line of test code.
Integration tests for anything touching a database, API, or external service. The real behavior, not a mock. Slower but far more reliable.
End-to-end tests for the three to five user journeys that must never break. Checkout, login, the critical path. A small number of these catches more regressions than hundreds of unit tests.
What makes testing culture stick
- Tests live next to the code they cover, not in a separate directory hierarchy
- Failing tests block merges. no exceptions for "we'll fix it later"
- New engineers write tests for their first feature, guided by someone senior
The culture part isn't technical. It's just consistency.