| name | testing-strategy |
| description | Testing philosophy and strategy. Use this when deciding what to test, naming tests, or identifying corner cases.
|
Skill: Testing Strategy
Testing Mindset
- Think like an adversary — imagine how the code could break and test those paths.
- Value over coverage — a test that proves real behavior beats a metric-inflating test.
Never write a test that cannot fail in a meaningful way.
- Readable by anyone — test names and body must tell a complete story. A failing test
must explain the problem without requiring a debugger.
When to Add a Test
Add a test only when it satisfies at least ONE of:
- It catches a real bug that could reach production.
- It documents a non-obvious contract (e.g. "returns empty list, never null").
- It guards a regression that has already occurred.
- It validates the interaction between two real components.
Do NOT add tests for:
- Trivial getters/setters with no logic.
- Behaviour already fully covered by an existing test.
- Happy-path-only tests when edge cases exist and are untested.
- Tests that always pass regardless of implementation.
Test Case Naming
Use the format TestUnit_Scenario_ExpectedOutcome:
TestParseConfig_MissingRequiredField_ReturnsError
TestParseConfig_ValidInput_ReturnsParsedResult
Sub-tests use plain, readable English:
"missing required field returns error"
"valid input with 3 items succeeds"
Anatomy of a Good Test
- Arrange — set up inputs and dependencies clearly; avoid hidden shared state.
- Act — single call to the unit under test.
- Assert — check the outcome and produce a message that explains the failure.
Keep each test focused on one behaviour. When multiple scenarios exist, use
table rows rather than separate functions.
Corner Cases Checklist
Before marking a feature tested, ask:
- What happens with a nil/null/zero/empty input?
- What happens at the boundary (first item, last item, exactly at a limit)?
- What happens when a dependency fails halfway through?
- What happens when the same operation runs concurrently?
- What happens with the largest valid input?
- What happens when required configuration is missing?
