JUnit - Understanding @ClassRule

The annotation @ClassRule can be used as an alternative to @Rule annotation.

It must be used on a static TestRule fields/methods.

The life cycle of such rule execution is on class level rather than on instance level, which is similar to the static methods annotated with @BeforeClass.

Let's understand how it works.

Example

In this example, we are going to reuse our PerformanceLogger from the last example.

public class MyTestClass {
  @ClassRule
  public static PerformanceLogger performanceLogger = new PerformanceLogger();

  @Test
  public void testMethod1() throws InterruptedException {
      System.out.println("running testMethod1()");
      Thread.sleep(200);
  }

  @Test
  public void testMethod2() throws InterruptedException {
      System.out.println("running testMethod2()");
      Thread.sleep(150);
  }

  @Test
  public void testMethod3() throws InterruptedException {
      System.out.println("running testMethod3()");
      Thread.sleep(100);
  }
}

mvn -q test -Dtest=MyTestClass

Output

d:\example-projects\junit\junit-class-rule>mvn -q test -Dtest=MyTestClass
running testMethod1()
running testMethod2()
running testMethod3()
Time taken for com.logicbig.example.MyTestClass: 454 milli sec

Example Project

Dependencies and Technologies Used:

• junit 4.12: JUnit is a unit testing framework for Java, created by Erich Gamma and Kent Beck.
• JDK 1.8
• Maven 3.3.9