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.

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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.

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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

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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)

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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)

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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?"

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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.

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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

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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

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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