org.junit
Annotation Type ClassRule

@Retention(value=RUNTIME)
@Target(value={FIELD,METHOD})
public @interface ClassRule

Annotates static fields that reference rules or methods that return them. A field must be public, static, and a subtype of TestRule. A method must be public static, and return a subtype of TestRule.

The Statement passed to the TestRule will run any BeforeClass methods, then the entire body of the test class (all contained methods, if it is a standard JUnit test class, or all contained classes, if it is a Suite), and finally any AfterClass methods.

The statement passed to the TestRule will never throw an exception, and throwing an exception from the TestRule will result in undefined behavior. This means that some TestRules, such as ErrorCollector, ExpectedException, and Timeout, have undefined behavior when used as ClassRules.

If there are multiple annotated ClassRules on a class, they will be applied in an order that depends on your JVM's implementation of the reflection API, which is undefined, in general. However, Rules defined by fields will always be applied before Rules defined by methods.

For example, here is a test suite that connects to a server once before all the test classes run, and disconnects after they are finished:

 @RunWith(Suite.class)
 @SuiteClasses({A.class, B.class, C.class})
 public class UsesExternalResource {
     public static Server myServer= new Server();

     @ClassRule
     public static ExternalResource resource= new ExternalResource() {
       @Override
       protected void before() throws Throwable {
          myServer.connect();
      }

      @Override
      protected void after() {
                myServer.disconnect();
      }
   };
 }
 

and the same using a method

 @RunWith(Suite.class)
 @SuiteClasses({A.class, B.class, C.class})
 public class UsesExternalResource {
     public static Server myServer= new Server();

     @ClassRule
     public static ExternalResource getResource() {
         return new ExternalResource() {
             @Override
             protected void before() throws Throwable {
                 myServer.connect();
             }

             @Override
             protected void after() {
                 myServer.disconnect();
             }
         };
     }
 }
 

For more information and more examples, see TestRule.

Since:

4.9