Unit Test Frameworks

Chapter 4. Writing Unit Tests

The previous chapters present a simple unit test framework and the fundamentals of xUnit. The unit test framework’s architecture is important to understand, but not something you have to think about often. Most of your time should be spent writing unit tests, implementing production code to make the tests pass, or refactoring. This chapter includes examples of common patterns used when writing unit tests, as well as related tips on unit test development.

The code examples in this chapter are unit tests of additional virtual library functionality, including looking up books by author and title, looking up multiple books by one author, and removing books from the library. The Library and Book code to implement the new features is given at the end of the chapter.

Types of Asserts

The code examples shown so far use plain asserts . These are the most generic type of test assertion, which take a Boolean condition that must evaluate to TRUE for the test to succeed. A plain assert, the unit test for the Library method removeBook( ), is shown in Example 4-1.

Example 4-1. Test method testRemoveBook( ) using a plain assert

LibraryTest.java
   public void testRemoveBook( ) {
      library.removeBook( "Dune" );
      Book book = library.getBook( "Dune" );
      assertTrue( book == null );
   }

If the method removeBook( ) is stubbed out, the test fails. The following test results report the failure:

> java junit.textui.TestRunner LibraryTests .....F. Time: 0.06 There was 1 failure: 1) testRemoveBook(LibraryTest)junit.framework.AssertionFailedError ...