claudia-testing

Claudia Testing Domain

Overview

Testing is about confidence, not coverage numbers. Test the things that would hurt if they broke. A 40% coverage suite that tests critical paths well beats a 95% coverage suite full of snapshot tests and trivial assertions.

The Test Pyramid: What Goes Where

What are you testing?
├── Pure logic, utilities, data transformations
│   └── Unit tests (fast, many, isolated)
├── API routes, database queries, component interactions
│   └── Integration tests (moderate speed, test real connections)
├── Critical user flows (signup, checkout, auth)
│   └── E2E tests (slow, few, high-value)
└── Not sure
    └── Ask: "If this broke in production, how bad would it be?"
        ├── Very bad → E2E test for the flow
        ├── Bad → Integration test
        └── Annoying → Unit test or skip it

Unit Tests

Test pure functions, business logic, utilities, data transformations, state machines. These should be fast (< 1ms each), have no I/O, no network, no database. If you need mocks to test it, it might not be a unit test.

Integration Tests

Test API route handlers with real middleware, database queries against a test database, component trees that interact (parent-child data flow), service layers that coordinate multiple modules. These can be slower and use real dependencies.

E2E Tests

Test only critical user flows: can a user sign up, log in, and do the core thing your app exists for? Keep these minimal. Every E2E test you add is a test you have to maintain against flakiness.

What NOT to Test

• Implementation details: Don't test that a function calls another function internally. Test the output.
• Framework internals: Don't test that React renders a div. React already tests that.
• Trivial getters/setters: getName() returning this.name doesn't need a test.
• 1:1 mock-heavy tests: If your test mocks everything the function touches, you're testing the mocks, not the code.
• CSS/styling: Visual regression tools exist, but manual review catches more real issues.
• Third-party libraries: Don't test that lodash.sortBy works. Test your code that uses it.