Radar

Overview

This skill improves test reliability and coverage without changing product behavior.

It focuses on adding the smallest useful tests, fixing instability, and increasing confidence in the system.

1. Choose the Right Target First

Before writing tests:

• Identify high-risk areas (edge cases, errors, async logic).
• Prioritize uncovered or weakly tested behavior.
• If unclear, ask what should be protected.
• Avoid testing low-impact or trivial code first.

Do not write tests without a clear purpose.

2. Test Behavior, Not Implementation

Write tests that validate what the system does, not how it is built.

Avoid:

• Testing private/internal functions directly
• Over-mocking internals
• Asserting implementation details

Prefer:

• Inputs → outputs
• Public interfaces
• Observable side effects

3. Keep Tests Simple and Isolated

Each test must:

• Have its own setup and cleanup
• Not depend on execution order
• Avoid shared mutable state

Guidelines:

• Use clear structure (Arrange → Act → Assert)
• Keep tests small (< 50 lines if possible)
• Use deterministic data (no randomness, no real time)

4. Fix Flaky Tests Properly

When tests fail intermittently:

• Find the root cause before fixing
• Common causes:
  • async timing issues
  • shared state
  • order dependency

Avoid:

• Adding arbitrary delays
• Blind retries

Prefer:

• Proper async handling (waitFor, retries with context)
• Isolation of state
• Deterministic timing (mocks, fake timers)

5. Add High-Value Coverage

Focus on:

• Edge cases (null, empty, limits)
• Error paths
• Branch conditions (true/false cases)

Do not:

• Chase coverage numbers blindly
• Add redundant tests

Ask:

"Does this test catch a real possible failure?"

6. Regression Safety First

When fixing bugs:

1. Write a test that fails (reproduces the bug)
2. Apply the fix
3. Ensure the test passes

Never fix bugs without locking them with a test.

Expected Behavior

This skill is working correctly if:

• Tests are stable (no flaky failures)
• Coverage improves in meaningful areas
• Tests remain simple and readable
• Bugs are protected with regression tests
• No unnecessary or redundant tests are added

Example Usage

User request: "Add tests for this function"

With this skill:

1. Identify missing edge cases
2. Add minimal high-value tests
3. Ensure isolation and determinism
4. Avoid over-testing internals

User request: "Tests are failing randomly"

With this skill:

1. Identify flaky root cause
2. Remove nondeterminism
3. Stabilize async behavior
4. Verify consistent results