Unbearable Test Code Smell

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Unbearable Test Code Smell

  1. 1. Unbearable Test Smells Steven Mak steven@odd-e.com www.odd-e.com twitter: stevenmak 1 Monday, 15 November 2010
  2. 2. Who am I? 2 Name: Steven Mak Agile Coach at Odd-e Lives in Hong Kong Agile/Scrum, TDD Coaching I love coding - Java, C/C++, PHP, Perl, C#, VB, and some weird languages Monday, 15 November 2010
  3. 3. Copy and Paste Code Long test codes are copied and pasted somewhere else with only a few lines changing 3 Monday, 15 November 2010
  4. 4. DRY Donʼt Repeat Yourself! Donʼt Repeat Yourself! Donʼt Repeat Yourself! Donʼt Repeat Yourself! Donʼt Repeat Yourself! Donʼt Repeat Yourself! Donʼt Repeat Yourself! Donʼt Repeat Yourself! 4 Monday, 15 November 2010
  5. 5. Not knowing the fixtures Some initialisation and clean up codes that are repeated in each tests... 5 Monday, 15 November 2010
  6. 6. What is fixture? TEST_GROUP (TEST_thisObject) { void setup() { } void teardown() { } }; 6 Monday, 15 November 2010
  7. 7. Duplication causing fragile tests Where is the duplication? EXPECT_LOG(“ABC error”); 7 Monday, 15 November 2010
  8. 8. Duplication causing fragile tests Where is the duplication? EXPECT_LOG(“ABC error”); So there is a line in code that prints this log message 8 Monday, 15 November 2010
  9. 9. Duplication causing fragile tests Put it under centralise header file: #define ABC_ERROR_WITH_EC “ABC error” The test will then look like: EXPECT_LOG(ABC_ERROR); 9 Monday, 15 November 2010
  10. 10. Over-Optimism? Tests that forgot to cover exceptional cases or just covered the easiest condition if (aaa() || bbb() || ccc() { ... } else { ... } 10 Monday, 15 November 2010
  11. 11. Tests donʼt have assertions TEST(TEST_GROUP, TEST_THIS) { runThisFunctionLaLaLa(); } 11 Monday, 15 November 2010
  12. 12. 12 What does it mean by 80% Unit Test Coverage? Monday, 15 November 2010
  13. 13. Why xUnits donʼt have CHECK_NOT_EQUAL? What is the problem with: CHECK(TRUE, xxx != 3); 13 Monday, 15 November 2010
  14. 14. Why xUnits donʼt have CHECK_NOT_EQUAL? What is the problem with: CHECK(TRUE, xxx != 3); Is there any good reason why you cannot know the output value? So, tell me what it is then. 14 Monday, 15 November 2010
  15. 15. OK, fine, so I use CHECK with a specific output value, what now? What is the problem with: CHECK(TRUE, xxx == 4); 15 Monday, 15 November 2010
  16. 16. OK, fine, so I use CHECK with a specific output value, what now? What is the problem with: CHECK(TRUE, xxx == 4); In most xUnits, we have LONGS_EQUAL telling you the actual value when it goes wrong instead of a “false” 16 Monday, 15 November 2010
  17. 17. 17 Do you know your xUnit harness? Monday, 15 November 2010
  18. 18. Further example try { readConfigurationFile(); assertTrue(true); } catch (IOException e) { assertTrue(false); e.printStackTrace(); } These are the places you know your team does not know the test harness. 18 Monday, 15 November 2010
  19. 19. 19 Some xUnit harness Java: JUnit .Net: NUnit C/C++: CppUTest PHP: PHPUnit Monday, 15 November 2010
  20. 20. Whatʼs wrong? What is the problem with: TEST(TEST_AIH, FAIL_BAD_PARAM) 20 Monday, 15 November 2010
  21. 21. Names donʼt really tell What is the problem with: TEST(TEST_AIH, FAIL_BAD_PARAM) Be more precise about how it triggered the failure 21 Monday, 15 November 2010
  22. 22. What names tell us? • Who - Name of the SUT class - Name of the method or feature being exercised • Input - Important characteristics of any input values - Anything relevant about the state • Output - The outputs expected - The expected post-exercise state 22 Monday, 15 November 2010
  23. 23. Conditional Test Logic? // verify Vancouver is in the list actual = null; i = flightsFromCalgary.iterator(); while (i.hasNext()) { FlightDto flightDto = (FlightDto) i.next(); if (flightDto.getFlightNumber().equals( expectedCalgaryToVan.getFlightNumber())) { actual = flightDto; assertEquals("Flight from Calgary to Vancouver", expectedCalgaryToVan, flightDto); break; } } 23 Monday, 15 November 2010
  24. 24. Tests that crash 50% of the time?!! 24 Monday, 15 November 2010
  25. 25. public void testFlightMileage_asKm2() throws Exception { // set up fixture // exercise constructor Flight newFlight = new Flight(validFlightNumber); // verify constructed object assertEquals(validFlightNumber, newFlight.number); assertEquals("", newFlight.airlineCode); assertNull(newFlight.airline); // set up mileage newFlight.setMileage(1122); // exercise mileage translator int actualKilometres = newFlight.getMileageAsKm(); // verify results int expectedKilometres = 1810; assertEquals( expectedKilometres, actualKilometres); // now try it with a canceled flight newFlight.cancel(); try { newFlight.getMileageAsKm(); fail("Expected exception"); } catch (InvalidRequestException e) { assertEquals( "Cannot get cancelled flight mileage", e.getMessage()); } } 25 Testing everything at a time Monday, 15 November 2010
  26. 26. Testing everything at a time public void testFlightMileage_asKm2() throws Exception { // set up fixture // exercise constructor Flight newFlight = new Flight(validFlightNumber); // verify constructed object assertEquals(validFlightNumber, newFlight.number); assertEquals("", newFlight.airlineCode); assertNull(newFlight.airline); // set up mileage newFlight.setMileage(1122); // exercise mileage translator int actualKilometres = newFlight.getMileageAsKm(); // verify results int expectedKilometres = 1810; assertEquals( expectedKilometres, actualKilometres); // now try it with a canceled flight newFlight.cancel(); try { newFlight.getMileageAsKm(); fail("Expected exception"); } catch (InvalidRequestException e) { assertEquals( "Cannot get cancelled flight mileage", e.getMessage()); } } 26 Comments as deodorant Monday, 15 November 2010
  27. 27. Testing everything at a time public void testFlightMileage_asKm2() throws Exception { // set up fixture // exercise constructor Flight newFlight = new Flight(validFlightNumber); // verify constructed object assertEquals(validFlightNumber, newFlight.number); assertEquals("", newFlight.airlineCode); assertNull(newFlight.airline); // set up mileage newFlight.setMileage(1122); // exercise mileage translator int actualKilometres = newFlight.getMileageAsKm(); // verify results int expectedKilometres = 1810; assertEquals( expectedKilometres, actualKilometres); // now try it with a canceled flight newFlight.cancel(); try { newFlight.getMileageAsKm(); fail("Expected exception"); } catch (InvalidRequestException e) { assertEquals( "Cannot get cancelled flight mileage", e.getMessage()); } } 27 Duplications with application logic? Monday, 15 November 2010
  28. 28. Inappropriate dependencies • Test setup depending on other tests files • A test file depending on another test file • Stub functions depending on other tests extern int reg_ecx; // in the stub program int reg_exc; // in SUT 28 Monday, 15 November 2010
  29. 29. What can we do? 29 Monday, 15 November 2010
  30. 30. Try: one test group per file But why canʼt? is it because of... ? 30 Monday, 15 November 2010
  31. 31. Test initialisation hard to read and shared among test groups in the same test file • Fixtures • Test Data Builder • Parameterised Creation • make-it-easy 31 Monday, 15 November 2010
  32. 32. Dont forget fixtures TEST_GROUP (TEST_thisObject) { void setup() { } void teardown() { } }; 32 Monday, 15 November 2010
  33. 33. Test Data Builder eth_data_buf ->setControl(2) ->withParameterA(3) ->build(); 33 Monday, 15 November 2010
  34. 34. Parameterised Creation @Before public void setUp() throws Exception { alice = new Person(); alice.setId(1L); alice.setFirstname("Alice"); alice.setLastname("Adams"); alice.setSsn("111111"); billy = new Person(); billy.setId(2L); billy.setFirstname("Billy"); billy.setLastname("Burke"); billy.setSsn("222222"); clark = new Person(); clark.setId(3L); clark.setFirstname("Clark"); clark.setLastname("Cable"); clark.setSsn("333333"); alice.isInLoveWith(billy); } 34 Monday, 15 November 2010
  35. 35. Parameterised Creation public class ParameterizedCreationMethodExample { private Person alice, billy, clark; @Before public void setUp() throws Exception { clark = createPerson("Clark", "Cable"); billy = createPerson("Billy", "Burke"); alice = createPerson("Alice", "Adams"); alice.isInLoveWith(billy); } private Person createPerson(String firstName, String lastName) { Person person = new Person(); person.setFirstname(firstName); person.setLastname(lastName); person.setId(UniqueNumber.next()); person.setSsn(String.valueOf(UniqueNumber.next())); return person; } @Test public void aliceShouldAcceptWhenProposedToByBilly() throws Exception { billy.proposeTo(alice); assertTrue(alice.isEngagedWith(billy)); } } 35 Monday, 15 November 2010
  36. 36. make-it-easy 36 http://code.google.com/p/make-it-easy/ Maker<Apple> appleWith2Leaves = an(Apple, with(2, leaves)); Maker<Apple> ripeApple = appleWith2Leaves.but(with(ripeness, 0.9)); Maker<Apple> unripeApple = appleWith2Leaves.but(with(ripeness, 0.125));         Apple apple1 = make(ripeApple); Apple apple2 = make(unripeApple);         Banana defaultBanana = make(a(Banana)); Banana straightBanana = make(a(Banana, with(curve, 0.0))); Banana squishyBanana = make(a(Banana, with(ripeness, 1.0))); Monday, 15 November 2010
  37. 37. Try: One assertion per test 37 Monday, 15 November 2010
  38. 38. Customised Assertions #define CHECK_OBJ(a,b) CHECK_OBJ(a,b, __FILE__,__FILE__) void CHECK_OBJ(struct* yourObj, struct* myObj, const char* file, int line) { if (structs are not equal) { SimpleString errorMessage = StringFromFormat( “My struct: %d, %p, %s”, myObj->d, myObj->p, myObj->s); FAIL_LOCATION(errorMessage.asCharString(), file, line); } } 38 Monday, 15 November 2010
  39. 39. At least: One concept per test 39 Monday, 15 November 2010
  40. 40. Hamcrest • Framework for writing declarative match criteria 40http://code.google.com/p/hamcrest/ String s = "yes we have no bananas today"; Matcher<String> containsBananas = new StringContains("bananas"); Matcher<String> containsMangoes = new StringContains("mangoes"); assertTrue(containsBananas.matches(s)); assertFalse(containsMangoes.matches(s)); assertThat(s, containsString("bananas")); assertThat(s, not(containsString("mangoes")); Or even better Monday, 15 November 2010
  41. 41. Meaningful Assertion Messages 41 • Donʼt repeat what the built-in test framework outputs to the console (e.g. name of the test method) • Donʼt repeat what the test name explains • If you donʼt have anything good to say, you donʼt have to say anything • Write what should have happened, or what failed to happen, and possibly mention when it should have happened Monday, 15 November 2010
  42. 42. Itʼs Design Smell!!! 42 Monday, 15 November 2010
  43. 43. Extra Constructor 43 public class LogFileMerge { private URL logFileA, logFileB; public LogFileMerge() { this(new URL("http://server1/system.log"), new URL("http://server2/system.log")); } LogFileMerge(URL a, URL b) { this.logFileA = a; this.logFileB = b; } } Monday, 15 November 2010
  44. 44. Test-Specific SubClass 44 public class CreditCardProcessing { public boolean isValid(String cardnumber) { return validationCodeMatches(cardnumber) && cardIsActive(cardnumber); } protected boolean validationCodeMatches(String cardnumber) { // validation logic omitted for brevity... } protected boolean cardIsActive(String cardnumber) { // access to merchant system's web service // omitted for brevity... } } Monday, 15 November 2010
  45. 45. Still not testable? 45 • Do you follow good design principles? Monday, 15 November 2010
  46. 46. Thinking 46 Test code is not second class citizen Good design principles apply: • Responsibility • Dependency • Low Coupling • High Cohesion • Indirection • Protected Variations Watch out for organisational dysfunction! Monday, 15 November 2010
  47. 47. References • Practical TDD and ATDD for Java Developers - Lasse Koskela • Growing OO Software, guided by tests - Steve Freeman • xUnit Test Patterns - Gerard Meszaros 47 Steven Mak steven@odd-e.com www.odd-e.com twitter: stevenmak Monday, 15 November 2010

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