Testing your code
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The document discusses testing Java code using test-driven development (TDD). It covers TDD basics like writing tests before code, unit testing individual functions, and automatically running tests frequently. It provides examples of how to structure unit tests with arrangements, actions, and assertions and use mocking to isolate dependencies. Guidelines are given for writing testable code and utilizing features of testing frameworks like parameterized tests, expected exceptions, and matchers.
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Example of TDD
Telephone field validator:
• Allowed characters:
• numbers: [0-9]
• minus, space: “-” , “ ”
• Length: 10 digits (ignore spaces and minuses)
• Leading and trailing spaces are allowed
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Testing your code
- 1. Exigen Services confidential Exigen Services confidential Testing your code For Java developers Anna Khasanova Anna.Khasanova@exigenservices.com 20 July 2015
- 2. Exigen Services confidential Agenda • Testing basics • TDD approach • Testing in action • Best practices 2
- 3. Exigen Services confidential What is a test? Why do we need it? • What is test? • Why do we need testing? • Automation 3
- 4. Exigen Services confidential Automatic testing Write once run often: • Write test once • Run frequently: • After each change • Continuous integration • No human input 4
- 5. Exigen Services confidential TDD THEORY What is Test Driven Development? 5
- 6. Exigen Services confidential Test Driven Development • Software development approach • Test before code • Test - code requirements 6
- 7. Exigen Services confidential Advantages • Increase requirements quality • Increase code quality • No unnecessary code 7
- 8. Exigen Services confidential New change request? 8 Test fails Write test Run test Test succeeds Design Write code Test succeeds Run test Test fails Whole story covered Test succeeds Refactor code Run test Test fails All tests succeed
- 9. Exigen Services confidential Bugfix? • Get bug report • Turn it into a test • Test should fail • Fix bug • Test should pass 9
- 10. Exigen Services confidential THE PRACTICE How should I work? How to write tests? 10
- 11. Exigen Services confidential What is Unit Test? • Automated test for • One business unit • One business case • Isolated 11
- 12. Exigen Services confidential Unit Test is • Small • Fast • Self documented 12
- 13. Exigen Services confidential 3 parts of Unit-test unitTest() { // set preconditions: “arrange” // call tested method: “act” // assert results are as expected: “assert” } 13
- 14. Exigen Services confidential Unit-Test libraries • xUnit – collective naming: dbUnit, htmlUnit, qUnit, etc. • Java: jUnit • Java: TestNG • Javascript: jasmine 14
- 15. Exigen Services confidential Example of TDD Telephone field validator: • Allowed characters: • numbers: [0-9] • minus, space: “-” , “ ” • Length: 10 digits (ignore spaces and minuses) • Leading and trailing spaces are allowed 15
- 16. Exigen Services confidential REAL LIFE Mock all dependencies 16
- 17. Exigen Services confidential We have a problem! • Method uses web service • or some other class/function • We don’t want to test it 17
- 18. Exigen Services confidential Mock • Fake implementation • We set what mock returns • Useful for unit-testing 18
- 19. Exigen Services confidential Mock libraries • Mockito • EasyMock • jMock 19
- 21. Exigen Services confidential Example @Test public void testGetSquarePicturesEmptyResult() { PicturesService testedService = new PicturesService(); Repository repository = mock(Repository.class); when(repository.getAllPictures()) .thenReturn(Collections.<Picture>emptyList()); testedService.setRepository(repository); Set<Picture> result = testedService.getSquarePictures(); assertTrue(result.isEmpty()); } 21 //create fake Repository, returning empty list of pictures
- 22. Exigen Services confidential How to verify external calls? • What to do if: • Tested method should call externals • We need to ensure that it was called? • Mocks scenario verification 22
- 23. Exigen Services confidential Example @Test public void testDeleteSquarePicturesEmptyResult() { PicturesService testedService = new PicturesService(); Repository repository = mock(Repository.class); Mockito.when(repository.getAllPictures()) .thenReturn(Collections.<Picture>emptyList()); testedService.setRepository(repository); testedService.deleteSquarePictures(); verify(repository, never()).deletePictures(any()); } 23
- 24. Exigen Services confidential How to verify arguments? • What to do if: • Mocked method is called with parameters • We need to test passed parameters? • Argument Captor • Matchers 24
- 25. Exigen Services confidential Example @Test public void testDeleteSquarePictures_captor() { … ArgumentCaptor<Iterable> captor = ArgumentCaptor.forClass(Iterable.class); verify(repository).deletePictures(captor.capture()); Iterable<Picture> result = captor.getValue(); … } 25
- 26. Exigen Services confidential How to verify exceptional cases? • What to do if: • Tested method should throw exception in some case • We need to test this case? • Expected exceptions @Test(expected = IllegalArgumentException.class) public void testFactorialNegative() { Factorial.factorial(-2); } 26
- 27. Exigen Services confidential How to verify exceptional cases? • What to do if: • We need to test time of execution? • Timeout parameter @Test(timeout = 1000) public void infinity() { while (true) ; } 27
- 28. Exigen Services confidential OTHER USEFUL FEATURES 28
- 29. Exigen Services confidential Other features: matchers Matchers • when(…), verify(…) • assertThat(…) • See hamcrest library • Write your own 29
- 30. Exigen Services confidential Other features: runners Test runners • @RunWith • Spring: SpringJUnit4ClassRunner • Parameterized • Any other 30
- 31. Exigen Services confidential SUMMARY. GUIDELINES. To sum this all up… 31
- 32. Exigen Services confidential Coverage • Coverage: what needs to be covered • Setters-getters 32
- 33. Exigen Services confidential Above all 1. Understand requirements 2. Commit your understanding • Java docs • Any other 33
- 34. Exigen Services confidential Unit test • One test – one case • Each use case – covered • Unit test != trash 34
- 35. Exigen Services confidential Write testable code • Statics are evil • Extract interfaces • One method must not do “everything” 35
- 36. Exigen Services confidential Use framework’s features • Parameterized tests • Expected exceptions, timeouts • Mock objects scenarios • Matchers 36
- 37. Exigen Services confidential Finally • Automatic testing – difficult to start, but… • Don’t give up! 37
- 38. Exigen Services confidential QUESTIONS? Your turn 38