Test Coverage

2 loại coverage chính

Code coverage

% code executed bởi test.

• Line coverage — line executed.
• Branch coverage — if/else branch covered.
• Function coverage — function called.
• Path coverage — all execution path (exponential, rarely 100%).

Tools: Istanbul (JS), Coverage.py, JaCoCo (Java), Slather (iOS).

Requirement coverage

% requirements covered by test case.

• Map: requirement ID → test case ID.
• Tools: TestRail, Xray, qTest.

Common targets

• Line coverage: 80%.
• Branch coverage: 70%.
• Critical user journey: 100%.
• Requirement: 100% for critical, 80% overall.

Anti-pattern

• 100% line coverage không = test tốt. Test có thể just call function, không assert.
• Chase coverage number → test trivial code (getter/setter).
• Skip difficult code (error handling) → low value coverage.

Gold standard

• Mutation testing — Stryker, PIT.
• Insert random bug → does test catch? Real signal of test quality.

Coverage trend

• Day 1: 30%.
• Sau onboarding: 60%.
• Mature: 80%.
• Diminishing return > 85%.

VN team practice

Banking app: > 80% mandatory. Startup: aim 60%, focus quality > quantity.

Coverage by code type

• Business logic: 90%+.
• UI: 60-70%.
• Generated code: skip from report.
• 3rd-party wrapper: 50%.