JUnit: @Before only for some test methods?

Question

I have some common set up code that I've factored out to a method marked with @Before. However, it is not necessary for all this code to run for every single test. Is there a way to mark it so the @Before method only runs before certain tests?

Answer 1

Just move out the tests that don't need the setup code into a separate test class. If you have some other code common to the tests that would be helpful to keep, move that out into a helper class.

Answer 2

@Nested + @BeforeEach

Totally agree with the point of moving the related code to an inner class. So here what I have done.

1. Create an inner class inside your test class
2. Annotate the inner class with @Nested
3. Move all the test methods you want to use in the inner class
4. Write the init code inside the inner class and annotate it with @BeforeEach

Here is the code:

class Testing {

    @Test
    public void testextmethod1() {
    
      System.out.println("test ext method 1");
    
    }
    
    @Nested
    class TestNest{
    
       @BeforeEach
       public void init() {
          System.out.println("Init");
       }
    
       @Test
       public void testmethod1() {
          System.out.println("This is method 1");
       }
    
       @Test
       public void testmethod2() {
          System.out.println("This is method 2");
       }
    
       @Test
       public void testmethod3() {
          System.out.println("This is method 3");
       }
        
     }

     @Test
     public void testextmethod2() {
    
         System.out.println("test ext method 2");
    
     }

}

Here is the output

test ext method 1
test ext method 2
Init
This is method 1
Init
This is method 2
Init
This is method 3

Note: I am not sure if this is supported in Junit4. I am doing this in JUnit5

Answer 3

It is possible to achieve also via Assume from JUnit. And then you can check the method name for which you want to process @Before.

public class MyTest {
     @Rule
     public TestName testName = new TestName();

     @Before
     public void setUp() {
       assumeTrue(testName.getMethodName().equals("myMethodName"));
       // setup follows
     }
}

Check the topic for more insights about @Rule.

Answer 4

Now that it's 2023, I'd recommend sticking with JUnit 5.x

I'd also say that this is probably a micro-optimization. I would not go to the effort until I measured my test time and saw that running the code when it wasn't necessary added a significant amount of time.

Answer 5

Not sure about @Before, but I recently came up with a strategy for @After block to run selectively. The implementation was straight forward. I have some flags set to default values as part of the test class. They are reset to default values in @Before class. In the class I need to do things specific to a flag, I set those flags & in @After I check for flag values to do the respective jobs.

Answer 6

JUnit 4.12 provide Enclosed Runner like

@RunWith(Enclosed.class) 
public class GlobalTest{

    @RunWith(MockitoJUnitRunner.class)
    public class InnerTest{
    
    }

}