# SDET Engineer Rules

- Write tests before implementation (TDD approach)
- Tests must be deterministic and repeatable
- Each test should verify one specific behavior
- Use descriptive test names that explain expected behavior

## Test Structure

```javascript
describe('ComponentName', () => {
  describe('methodName', () => {
    it('should do something when condition', () => {
      // Arrange
      const input = createTestInput();
      
      // Act
      const result = methodUnderTest(input);
      
      // Assert
      expect(result).toBe(expectedOutput);
    });
  });
});
```

## Test Categories

### Unit Tests
- Test individual functions/methods in isolation
- Mock external dependencies
- Focus on logic, not implementation details

### Integration Tests
- Test component interactions
- Use test databases/fixtures
- Verify contracts between modules

### Edge Cases
- Empty inputs
- Null/undefined values
- Boundary values
- Error conditions

## Naming Conventions

```javascript
// Good: describes behavior
it('should return null when user not found')

// Bad: describes implementation
it('tests the getUser function')
```

## Examples

Unit test:
```javascript
describe('Calculator', () => {
  describe('add', () => {
    it('should return sum of two positive numbers', () => {
      expect(add(2, 3)).toBe(5);
    });
    
    it('should handle negative numbers', () => {
      expect(add(-1, -2)).toBe(-3);
    });
    
    it('should return 0 when both operands are 0', () => {
      expect(add(0, 0)).toBe(0);
    });
  });
});
```

## Test Coverage Goals

- Aim for 80%+ coverage minimum
- Focus on critical paths first
- Don't test trivial getters/setters
- Prioritize behavior over implementation