xUnit Test Patterns

Test Goals

  • Defect Localization: tells you what specifically went wrong
  • Repeatable Test: can be run many times in a row
  • Tests as Documentation: should be readable

Test Smells

  • Conditional Test Logic: some test code may or may not be executed
    • Production Logic in Test: duplicates the production code, not verifying anything
    • Related: Flexible Test
  • Erratic Test: sometimes pass and sometimes fail
    • A cause: Interacting Test: tests depend on other tests in some way. Goal: test isolation.
    • A cause: Nondeterministic Test
  • Fragile Test: fails when seemingly-unrelated code is changed
  • Hard-to-Test Code: (self-explanatory)
  • High Test Maintenance Cost: effort keeping tests passing is more than the benefit
  • Obscure Test: difficult to understand at a glance
    • Eager Test: verifies too much in one test
    • Incorrect amount of detail
      • Irrelevant Information: data not necessary to understand the test set up inside the test
      • Mystery Guest: data necessary to understand the test set up outside the test
    • Indirect Testing: checked via interacting with a separate object


  • Calculated Value: Meszaros considers it a pattern, I generally consider it a smell.
  • Fixture
    • Fresh Fixture: setting up a new fixture for each test.
    • General Fixture: larger than needed to verify the functionality. (Could consider this a smell.)
    • Minimal Fixture: smallest and simplest fixture possibile to verify the functionality.
    • Shared Fixture: reusing the same fixture for multiple tests. (Could consider this a smell.)
  • Hard-Coded Test Data: solves production logic. Meszaros says it’s a smell, but then says “better to enumerate the sets of precalculated values” to solve production logic.
  • Setup
    • In-Line Setup: done in the test function itself
    • Delegated Setup: explicitly call functions to set up the data
      • Parameterized Creation Method: (factories)
    • Implicit Setup: setUp() / beforeEach()
  • Single-Condition Tests: verify one condition per test