<critical_constraints> ❌ NO tests without edge cases ❌ NO generic assertions (assertTrue) → use specific (assertEqual, toEqual) ❌ NO test dependencies → each test must be independent ✅ MUST follow Arrange-Act-Assert (AAA) pattern ✅ MUST mock external dependencies (APIs, DB, filesystem) ✅ MUST use descriptive test names (what + expected outcome) </critical_constraints>

<test_categories>

• Normal cases: typical usage

• Edge cases: empty, zero, max, boundary

• Error cases: invalid input, exceptions

• Type edges: None/null, wrong types

• Performance: large inputs (if applicable) </test_categories>

def test_edge_empty(self): assert func([]) == []

def test_error_raises(self): with pytest.raises(ValueError): func(invalid)

JavaScript (Jest)

describe('functionName', () => {
  it('should return X when Y', () => {
    expect(func(input)).toBe(expected);
  });
  
  it('should throw on invalid', () => {
    expect(() => func(null)).toThrow(TypeError);
  });
});