6.3 Organizing test cases into test suites

6.3 Organizing test cases into test suites

The previous section shows how to define new tests. This section describes how to organize test cases into test suites.

6.3.1 A cookbook recipe for composing a test suite

The recipe 'JUnit 1.2: How to compose a test suite' completes the set of recipes that guide the principal adaptation of JUnit. The TestSuite class applies the Composite construction principle, except that the generalization is fixed (see Figure 6.3). This means that no additional direct subclass of Test shall be defined in the application.^[1] For that reason, a JUnit adaptation only defines subclasses of TestCase.

^[1] Since Test is an interface, this means that no additional direct implementations of the interface should be defined. In this case, the only valid implementations for Test are TestCase and TestSuite.

A method suite() is used to define new test suites. For convenience, it can be defined as a static method in a TestCase subclass. Figure 6.12 shows a sequence diagram which illustrates how a test suite is created. The method suite() creates a TestSuite object and adds the set of test cases by invoking addTest() for each test case or test suite object that should be part of the test suite.

Figure 6.12. Creating test suites

Table 6.6 describes the steps for defining a JUnit test suite. If inner classes have been used to define test cases, then the instances of inner subclasses of a test case have to be composed in a test suite. Thus, the previous recipe 'JUnit 1.1A' and the presented 'JUnit 1.2' are to some extent intertwined.

When JUnit is launched, for example through a Java command line interface, it takes the name of a TestCase subclass as parameter, invokes its suite() method getting a test suite object as result, and invokes the run() method on that test suite.

Table 6.6. Cookbook recipe for composing a test suite

Recipe 'JUnit 1.2: How to compose a test suite'
Intent	A number of tests have been defined and shall be composed to a single test suite. A new test suite shall combine a number of already existing tests and test suites.
Classes	TestSuite and TestCase.
Steps to Apply	Identify the tests and test suites to be grouped together. What common characteristics or purpose do they have? Should the new tests be added to an existing test suite definition? If so, then include appropriate code for adding them in that suite by extending its suite() method. Otherwise, introduce a static method called "suite()" returning a Test object and locate it in an appropriate TestCase class. In the following the code for method suite() is discussed. Create a new TestSuite object. If each test case is defined using recipe JUnit 1.1 (therefore in a single class), then just instantiate each of the classes and add these objects to the test suite. Otherwise, we assume the new tests are located as methods in the same class. Then use the Adapter technique of anonymous inner subclasses to map each method to runTest() and add the resulting objects to the test suite. If the new test suite is to contain other test suites as well, add those in the same way as the other tests.
Discussion	In addition to creating class-wide test suites, it is often useful to compose package, subsystem and finally system-wide test suites. Their possibly overlapping contents of tests make them less manageable over time. However, it might be worthwhile to define short life test suites that focus on particular features of the system if the overall runtime of a complete test suite is considerable.

6.3.2 Adaptation of a sample test suite

Based on the recipe 'JUnit 1.2: How to compose a test suite', we derive a compact suite() implementation as shown in Example 6.7.

Example 6.7 Creating a test suite in the suite() method of class ComplexTest

 public static Test suite() {       TestSuite suite = new TestSuite();       suite.addTest(new ComplexTest       ("testAddZeroZero") {             protected void runTest()             { this.testAddZeroZero(); }       });       suite.addTest(new       ComplexTest("testAddCommuting"){             protected void runTest()            { this.testAddCommuting(); }       } );       suite.addTest(new ComplexTest("testEquals"){        protected void runTest()       { this.test Equals();}       });       return suite; }