Test cases in inner classes with JUnit

Question

I read about Structuring Unit Tests with having a test class per class and an inner class per method. Figured that seemed like a handy way to organize the tests, so I tried

Answer 1

I've had success with Nitor Creation's Nested Runner as well.

How to use Nitor Creation's Nested Runner

There is a post explaining it here:

Add this dependency:

<dependency>
    <groupId>com.nitorcreations</groupId>
    <artifactId>junit-runners</artifactId>
    <version>1.2</version>
    <scope>test</scope>
</dependency>

And a @RunWith to your test:

import com.nitorcreations.junit.runners.NestedRunner
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import static org.junit.Assert.*;
  
@RunWith(NestedRunner.class)
public class RepositoryUserServiceTest {
           
    public class RegisterNewUserAccount {
     
        public class WhenUserUsesSocialSignIn {
             
            public class WhenUserAccountIsFoundWithEmailAddress {
                 
                @Test
                public void shouldThrowException() {
                     assertTrue(true);
                }
            }
         
        }
    }
}

PS: The example code has been taken and modified from the above blog post

Answer 2

public class ServicesTest extends TestBase {

   public static class TestLogon{

       @Test
       public void testLogonRequest() throws Exception {
         //My Test Code
       }
   }
}

Making the inner class static works for me.

Answer 3

In JUnit 5, you simply mark non-static inner classes as @Nested:

import org.junit.jupiter.api.Nested;
import org.junit.jupiter.api.Test;

public class DogTests {
    @Nested
    public class BarkTests {
        @Test
        public void quietBark_IsAtLeastAudible() { }

        @Test
        public void loudBark_ScaresAveragePerson() { }
    }

    @Nested
    public class EatTests {
        @Test
        public void normalFood_IsEaten() { }

        @Test
        public void badFood_ThrowsFit() { }
    }
}

Answer 4

I think some of the answers might be for older versions of JUnit. In JUnit 4 this worked for me:

    @RunWith(Suite.class)
    @Suite.SuiteClasses({ DogTests.BarkTests.class, DogTests.EatTests.class })
    public class DogTests
    {
        public static class BarkTests
        {
            @Test
            public void quietBark_IsAtLeastAudible() { }

            @Test
            public void loudBark_ScaresAveragePerson() { }
        }

        public static class EatTests
        {
            @Test
            public void normalFood_IsEaten() { }

            @Test
            public void badFood_ThrowsFit() { }
        }
    }

Answer 5

You should annontate your class with @RunWith(Enclosed.class), and like others said, declare the inner classes as static:

@RunWith(Enclosed.class)
public class DogTests
  {
  public static class BarkTests
  {
    @Test
    public void quietBark_IsAtLeastAudible() { }

    @Test
    public void loudBark_ScaresAveragePerson() { }
  }

  public static class EatTests
  {
    @Test
    public void normalFood_IsEaten() { }

    @Test
    public void badFood_ThrowsFit() { }
  }
}