Class Index

If you allocate expensive external resources in a BeforeClass method you need to release them after all the tests in the class have run. 

Sometimes several tests need to share computationally expensive setup (like logging into a database). 

 // These tests all pass. 

 public static class UsesExternalResource {
 	Server myServer= new Server();
 
 	@Rule
 	public ExternalResource resource= new ExternalResource() {
 		@Override
 		protected void before() throws Throwable {
 			myServer.connect();
 		};
 
 		@Override
 		protected void after() {
 			myServer.disconnect();
 		};
 	};
 
 	@Test
 	public void testFoo() {
 		new Client().run(myServer);
 	}
 }
 

Sometimes you want to temporarily disable a test or a group of tests. 

If you need to respond to the events during a test run, extend RunListener and override the appropriate methods. 

 public static class HasTempFolder {
 	@Rule
 	public TemporaryFolder folder= new TemporaryFolder();
 
 	@Test
 	public void testUsingTempFolder() throws IOException {
 		File createdFile= folder.newFile("myfile.txt");
 		File createdFolder= folder.newFolder("subfolder");
 		// ... 

The Test annotation tells JUnit that the public void method to which it is attached can be run as a test case. 

A TestSuite is a Composite of Tests. 

 public static class HasGlobalTimeout {
 	public static String log;
 
 	@Rule
 	public MethodRule globalTimeout= new Timeout(20);
 
 	@Test
 	public void testInfiniteLoop1() {
 		log+= "ran1";
 		for (;;) {
 		}
 	}
 
 	@Test
 	public void testInfiniteLoop2() {
 		log+= "ran2";
 		for (;;) {
 		}
 	}
 }
 

     public static class ErrorLogVerifier() {
        private ErrorLog errorLog = new ErrorLog();
     
        @Rule
        public MethodRule verifier = new Verifier() {
           @Override public void verify() {
              assertTrue(errorLog.isEmpty());
           }
        }
        
        @Test public void testThatMightWriteErrorLog() {
           // ...