Unit Testing & Testability

Transcription

1 CMPT 473 Software Quality Assurance Unit Testing & Testability Nick Sumner - Fall 2014

2 Levels of Testing Recall that we discussed different levels of testing for test planning: Unit Tests Integration Tests System Tests 2

3 Levels of Testing Recall that we discussed different levels of testing for test planning: Unit Tests Integration Tests System Tests The simplest of these is Unit Testing Testing the smallest possible fragments of a program 3

4 Unit Testing Try to ensure that the functionality of each component works in isolation 4

5 Unit Testing Try to ensure that the functionality of each component works in isolation Unit Test a car: Wheels work. Steering wheel works... 5

6 Unit Testing Try to ensure that the functionality of each component works in isolation Unit Test a car: Wheels work. Steering wheel works... Integration Test a car: Steering wheel turns the wheels... 6

7 Unit Testing Try to ensure that the functionality of each component works in isolation Unit Test a car: Wheels work. Steering wheel works... Integration Test a car: Steering wheel turns the wheels... System Test a car: Driving down the highway with the air conditioning on works... 7

8 Unit Testing Try to ensure that the functionality of each component works in isolation Unit Test a car: Wheels work. Steering wheel works... Integration Test a car: Steering wheel turns the wheels... System Test a car: Driving down the highway with the air conditioning on works... Not testing how well things are glued together. 8

9 Unit Testing Try to ensure that the functionality of each component works in isolation Unit Test a car: Wheels work. Steering wheel works... Integration Test a car: Steering wheel turns the wheels... System Test a car: Driving down the highway with the air conditioning on works... Not testing how well things are glued together. Why? How is this beneficial? 9

10 Unit Tests A dual view: They specify the expected behavior of individual components 10

11 Unit Tests A dual view: They specify the expected behavior of individual components An executable specification 11

12 Unit Tests A dual view: They specify the expected behavior of individual components An executable specification Can even be built first & used to guide development Usually called Test Driven Development 12

13 Unit Tests A dual view: They specify the expected behavior of individual components An executable specification Can even be built first & used to guide development Usually called Test Driven Development Have any of you experienced this in your jobs? 13

14 Unit Tests Some guiding principles: Focus on one component in isolation Be simple to set up & run Be easy to understand 14

15 Unit Tests Some guiding principles: Focus on one component in isolation Be simple to set up & run Be easy to understand Usually managed by some automating framework 15

16 Unit Tests Some guiding principles: Focus on one component in isolation Be simple to set up & run Be easy to understand Usually managed by some automating framework What frameworks have you used to write unit tests? 16

17 JUnit Widely used unit testing framework for Java And I know that you should have seen it before 17

18 JUnit Widely used unit testing framework for Java And I know that you should have seen it before We'll use it to drive our discussion, but its features exist in other frameworks, too. What features do your unit testing frameworks provide? 18

19 JUnit Basic Features 19

20 JUnit Basic Features Per class set up & tear 20

21 JUnit Basic Features Per class set up & tear Per test set up & tear 21

22 JUnit Basic Features Per class set up & tear Per test set up & tear Test identification & (expected=exception.class) (timeout=100) 22

23 JUnit Basic Features Per class set up & tear Per test set up & tear Test identification & (expected=exception.class) (timeout=100) Test 23

24 JUnit Basic Features Per class set up & tear Per test set up & tear Test identification & (expected=exception.class) (timeout=100) Test Expectations assertequals, asserttrue, assertfalse, assertnull,... 24

25 JUnit Let's work through a simple example (There shouldn't be anything new here, but it should be a refresher if you haven't seen it in awhile) 25

26 Testability What makes testing hard? Not just difficult to get adequacy What makes it difficult to write tests? 26

27 Testability What makes testing hard? Not just difficult to get adequacy What makes it difficult to write tests? Dependencies Connections between classes 27

28 Testability What makes testing hard? Not just difficult to get adequacy What makes it difficult to write tests? Dependencies Connections between classes Singletons 28

29 Testability What makes testing hard? Not just difficult to get adequacy What makes it difficult to write tests? Dependencies Connections between classes Singletons Nondeterminism 29

30 Testability What makes testing hard? Not just difficult to get adequacy What makes it difficult to write tests? Dependencies Connections between classes Singletons Nondeterminism Static binding 30

31 Testability What makes testing hard? Not just difficult to get adequacy What makes it difficult to write tests? Dependencies Connections between classes Singletons Nondeterminism Static binding Mixing construction & application logic... 31

32 Testability What makes testing hard? Not just difficult to get adequacy What makes it difficult to write tests? Dependencies Connections between classes Singletons Nondeterminism Static binding Mixing construction & application logic... But solutions exist! You can design code to be testable! 32

33 Testability (by example) Let's work together to improve some difficult to test code... 33

34 Testability Keys things to notice: Mocks & stubs allow us to isolate components under test 34

35 Testability Keys things to notice: Mocks & stubs allow us to isolate components under test Dependency Injection allows us to use mocks and stubs as necessary 35

36 Testability Keys things to notice: Mocks & stubs allow us to isolate components under test Dependency Injection allows us to use mocks and stubs as necessary But doing this can lead to a lot more work and boilerplate code when written by hand 36

37 Testability Keys things to notice: Mocks & stubs allow us to isolate components under test Dependency Injection allows us to use mocks and stubs as necessary But doing this can lead to a lot more work and boilerplate code when written by hand Given dependency injection, what happens to the way we create objects? 37

38 Testability Keys things to notice: Mocks & stubs allow us to isolate components under test Dependency Injection allows us to use mocks and stubs as necessary But doing this can lead to a lot more work and boilerplate code when written by hand Given dependency injection, what happens to the way we create objects? How might we mitigate boilerplate issues? 38

39 Mocking Framework Example Frameworks exist that can automate the boilerplate behind: 39

40 Mocking Framework Example Frameworks exist that can automate the boilerplate behind: Mocking e.g. Mockito, Jmock, etc. [DEMO] 40

41 Mocking Framework Example Frameworks exist that can automate the boilerplate behind: Mocking e.g. Mockito, Jmock, etc. Dependency Injection e.g. Google Guice, Pico Container, etc. 41