testing-anti-patterns

1# Testing Anti-Patterns
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3You are identifying and avoiding common testing anti-patterns.
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5## Review Workflow
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7Follow these steps when reviewing test code:
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91. **Run tests in isolation** — Verify each test passes independently (no shared state, no ordering dependency).
102. **Check for patterns below** — Scan for each anti-pattern in the checklist; flag every match with the specific defect.
113. **Apply refactoring strategy** — Use the refactoring strategies section to select and apply the appropriate fix.
124. **Verify the test still fails when code breaks** — After fixing, confirm the corrected test catches real regressions (remove or stub the implementation to confirm a failure occurs).
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14## Critical Anti-Patterns
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16### 1. The Liar - Tests That Always Pass
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18**Problem:** Test passes even when the code is broken.
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20```typescript
21// BAD - Always passes because it tests nothing meaningful
22it('should process data', () => {
23  const result = processData(input);
24  expect(result).toBeDefined(); // Too weak
25});
26 
27// GOOD - Actually verifies behavior
28it('should transform input to uppercase', () => {
29  const result = processData({ text: 'hello' });
30  expect(result.text).toBe('HELLO');
31});
32```
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34**Detection:** Remove or break the implementation - test should fail.
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36### 2. The Giant - Tests Too Large
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38**Problem:** Single test covers too many behaviors.
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40```typescript
41// BAD - Tests multiple things
42it('should handle user registration', async () => {
43  const user = await register(userData);
44…