Unit testing basics & more...

Transcription

1 Unit testing basics & more... by Papapetrou P.Patroklos Twitter hashtag : Thessaloniki Java Meetup - December 2014

2 Agenda Unit testing introduction Differences with other types of tests Key concepts Rules - things to remember A developer s toolset Live coding - hmm unit testing actually

3 Unit testing? Why bother? Code without tests is bad code. It doesn t matter how well written it is; it doesn t matter how pretty or object-oriented or well-encapsulated it is. With tests, we can change the behavior of our code quickly and verifiably. Without them, we really don t know if our code is getting better or worse. Michael Feathers Working Effectively With Legacy Code (2004)

4 Unit testing? Why bother? Code without unit tests is like American breakfast without eggs & bacon. Patroklos Papapetrou (2014)

5

6 What is unit testing? A practice of testing certain functions and areas or units of our code.

7 Advantages Identify failures in our algorithms and/or logic Approaching development from a unit testing perspective is that you'll likely be writing code that is easy to test Prevent future changes from breaking functionality ( safety pillow )

8 Unit testing vs?? We are here

9 (Good) Unit tests characteristics Run fast Isolated Repeatable Automatable Easy to write Easy to understand

10 Unit test structure Setup 1 Prepare input 2 Invoke method 3 Tear down Assert output 4 5

11 Assertions? What is that? Assertion -> A way to validate expected output / behavior of a method Examples Assert.assertEquals (a, b) Assert.assertTrue ( bool ) Each unit test should include only one assertion

12

13 Mocks / Stubs / Fakes Simulated objects that mimic the behavior of real objects in controlled ways.

14 Best Practices - Readability Setup and teardown methods are not abused. It s better to use factory methods for readability Each test tests one thing only Check for good and consistent naming conventions Make sure that only meaningful assert messages are used, or none at all (meaningful test names are better)

15 Best Practices - Readability Asserts are separated from actions (different lines). Tests don t use magic strings and values as inputs. use the simplest inputs possible to prove your point. There is consistency in location of tests. make it easy to find related tests for a method, or a class, or a project.

16 Best Practices - Maintainability Unit tests are isolated from each other and repeatable Testing private or protected methods is not the norm (public is always better) Tests are not over-specified State-based testing is preferred over using interaction testing

17 Best Practices - Maintainability Strict mocks are used as little as possible (leads to over specification and fragile tests) There is no more than one mock per test Tests do not mix mocks and regular asserts in the same test (testing multiple things)

18 Best Practices - Maintainability Unit Tests verify mock calls only on the single mock object in the test, and not on all the fake objects in the tests Unit Tests verify only on a single call to a mock object. Verifying multiple calls on a mock object is either over specification or testing multiple things.

19 Best Practices - Trust Tests does not contain logic or dynamic values Check coverage by playing with values (booleans or constants) Unit tests are separated from integration tests Unit tests don t use things that keep changing in a unit test (like DateTime.Now ). Use fixed values.

20 Best Practices - Trust Unit tests don t assert with expected values that are created dynamically - you might be repeating production code. Unit tests should not do exception handling.

21 Java Developer s toolset Basic Framework -> JUnit VS TestNG Mocking Framework -> Mockito VS PowerMock VS EasyMock Assertions Framework -> Hamcrest Matchers VS Fest Assert VS AssertJ My Choice -> JUnit + Mockito + PowerMockito + AssertJ

22 Let s write some tests

23 References JUnit : TestNG : Mockito : PowerMock : PowerMockito : com/p/powermock/wiki/mockitousage13 EasyMock :

24 References Hamcrest Matchers : Fest Assertions : AssertJ: