nw-test-refactoring-catalog

Test Refactoring Catalog

Test Code Smells (Full Detail)

L1 Readability Smells

Obscure Test

• Problem: test name does not reveal business scenario being tested
• Detection: generic names like Test1(), ProcessOrderTest(), or names requiring reading test body to understand
• Solution: rename to Given_When_Then or should_do_expected_thing_when_condition format

Before: public void Test1() { /* ... */ }
After:  public void ProcessOrder_PremiumCustomer_AppliesCorrectDiscount() { /* ... */ }

Hard-Coded Test Data

• Problem: magic numbers and strings obscure business rules being tested
• Detection: numbers like 1000, 0.15, strings without explanation
• Solution: extract to named constants that reveal business meaning

Before: Assert.Equal(850, result.Total);  // What discount?
After:  const decimal EXPECTED_TOTAL = 1000 * (1 - 0.15m);
        Assert.Equal(EXPECTED_TOTAL, result.Total);

Assertion Roulette

• Problem: multiple assertions without messages make failures unclear
• Detection: multiple Assert.* calls without message parameter
• Solution: add descriptive message to each assertion explaining expected business outcome

L2 Complexity Smells

Eager Test

• Problem: single test verifies multiple unrelated behaviors
• Detection: multiple arrange/act/assert cycles or assertions testing different concerns
• Solution: split into focused tests, one per business scenario

Before: ProcessOrderTest() { /* tests discount AND shipping AND tax */ }
After:  ProcessOrder_AppliesDiscount()
        ProcessOrder_CalculatesShipping()
        ProcessOrder_CalculatesTax()

Prefer parameterized tests for variations of the same behavior.

Test Code Duplication

• Problem: repeated test setup logic across multiple tests
• Detection: same object creation, mock setup, or data builders copied in 3+ tests
• Solution: extract helper methods

Extract: CreatePremiumCustomer(), CreateHighValueOrder()

Conditional Test Logic

• Problem: if/switch statements in test code make tests non-deterministic
• Detection: if, switch, for loops in test methods
• Solution: replace with parameterized tests

# Before: if/else in test
# After:
@pytest.mark.parametrize("input,expected", [...])
def test_behavior(input, expected): ...

L3 Organization Smells

Mystery Guest

• Problem: test depends on external files or hidden dependencies
• Detection: File.ReadAllText, database queries, external config in tests
• Solution: inline test data or make dependency explicit in test setup

Test Class Bloat

• Problem: single test class contains tests for multiple unrelated concerns
• Detection: test class with 15+ tests covering different features
• Solution: split by feature

Before: UserServiceTests (31 tests)
After:  UserAuthTests, UserProfileTests, UserNotificationTests

General Fixture

• Problem: shared fixture used by tests with different needs
• Detection: SetUp method creates data used by only some tests
• Solution: move to per-test setup methods or test-specific fixtures

For production code refactoring techniques and mechanics, load the progressive-refactoring skill.