add-test-coverage

Add Test Coverage

Test existing contracts. Focus on what the code does for consumers, not how it works internally.

Procedure

1. Identify untested contracts

Read the module's public interface: exports, function signatures, return types. These are the contracts to test. Skip internal helpers unless they encode critical business logic.

2. Write tests for behavior

For each contract:

• What does a consumer expect when calling with valid input?
• What happens with edge cases (empty, null, boundary values)?
• What error conditions exist?

Name each test by the behavior it verifies, not the function it calls.

3. Verify coverage delta

Run tests with coverage using the project's coverage command (check project CLAUDE.md). Compare per-file coverage before and after. Every new test should increase coverage for the target module.

Running Tests

• Environment errors before code errors — check sandbox, deps, and cwd first
• Sandbox blocks tests needing file writes, network, or env vars — disable when needed
• Compare test counts and failures against baseline

Red Flags

• Testing implementation (mocking internals) instead of contracts
• Test would break if internals were refactored
• Cannot name the specific regression this test catches
• No one would notice if this test were deleted
• Testing type checks or instanceof assertions — the compiler handles these
• Testing framework behavior instead of your code
• Testing trivial getters and setters with no logic