## Summary of Changes in version 4.7

### Rules

- Rules allow very flexible addition or redefinition of the behavior of each test method in a test class. Testers can reuse or extend one of the provided Rules below, or write their own.

  For more on this feature, see http://www.threeriversinstitute.org/blog/?p=155

- The TemporaryFolder Rule allows creation of files and folders that are guaranteed to be deleted when the test method finishes (whether it passes or fails):

  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");
          // ...
      }

  }

- ExternalResource is a base class for Rules (like TemporaryFolder) that set up an external resource before a test (a file, socket, server, database connection, etc.), and guarantee to tear it down afterward:

  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);
      }

  }

- The ErrorCollector Rule allows execution of a test to continue after the first problem is found (for example, to collect all the incorrect rows in a table, and report them all at once):

  public static class UsesErrorCollectorTwice { @Rule public ErrorCollector collector= new ErrorCollector();

      @Test public void example() {
          collector.addError(new Throwable("first thing went wrong"));
          collector.addError(new Throwable("second thing went wrong"));
      }

  }

- Verifier is a base class for Rules like ErrorCollector, which can turn otherwise passing test methods into failing tests if a verification check is failed

  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() { // ... } }

- TestWatchman is a base class for Rules that take note of the testing action, without modifying it. For example, this class will keep a log of each passing and failing test:

  public static class WatchmanTest { private static String watchedLog;

      @Rule
      public MethodRule watchman= new TestWatchman() {
          @Override
          public void failed(Throwable e, FrameworkMethod method) {
              watchedLog+= method.getName() + " "
                      + e.getClass().getSimpleName() + "\n";
          }

      @Override
      public void succeeded(FrameworkMethod method) {
          watchedLog+= method.getName() + " " + "success!\n";
      }

      };

      @Test
      public void fails() {
          fail();
      }

      @Test
      public void succeeds() {
      }

  }

- The TestName Rule makes the current test name available inside test methods:

  public class NameRuleTest { @Rule public TestName name = new TestName();

      @Test public void testA() {
          assertEquals("testA", name.getMethodName());
      }

      @Test public void testB() {
          assertEquals("testB", name.getMethodName());
      }

  }

- The Timeout Rule applies the same timeout to all test methods in a class:

  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(;;) {}
      }

  }

- The ExpectedException Rule allows in-test specification of expected exception types and messages:

  public static class HasExpectedException { @Rule public ExpectedException thrown= ExpectedException.none();

      @Test
      public void throwsNothing() {

      }

      @Test
      public void throwsNullPointerException() {
          thrown.expect(NullPointerException.class);
          throw new NullPointerException();
      }

      @Test
      public void throwsNullPointerExceptionWithMessage() {
          thrown.expect(NullPointerException.class);
          thrown.expectMessage("happened?");
          thrown.expectMessage(startsWith("What"));
          throw new NullPointerException("What happened?");
      }

  }

### Timeouts

- Tests that time out now show the stack trace of the test thread.

### Matchers

- Due to typing incompatibilities, JUnit is still including the 1.1 release of hamcrest. This is not a change from 4.6, but is a change from pre-beta releases of 4.7. Due to this incompatibility, tests using Hamcrest 1.2 must still use the MatcherAssert.assertThat method from Hamcrest, not Assert.assertThat from JUnit.

### Docs

- Javadocs now link to online JDK javadocs (bug 2090230)
- Parameterized runner javadocs improved (bug 2186792)
- Fixed Javadoc code sample for AfterClass (2126279)
- Fixed Javadoc for assertArraysEqual(float[], float[])

### Bug fixes

- Fixed: BaseTestRunner.getTest() requires class to extend TestCase (1812200)
- Fixed: Suite does not allow for inheritance in annotations (2783118)
- Fixed: ParallelComputer skipped tests that took longer than 2 seconds