junit - how to combine @RunWith with @RunWith(Parameterized.class)

Question

I implemented a runner class A.class inherited from BlockJUnit4ClassRunner so that I can annotate tests with @RunWith(A.class). At the same time, sb. else annotate the tests with RunWith(Parameterized.class). It is obvious we cannot use two @RunWith at the same time.

How to solve this problem? or how to merge these two @RunWith?

Answer 1

I believe this does what you want:

package so.junit.runner;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.model.InitializationError;
import org.junit.runners.parameterized.BlockJUnit4ClassRunnerWithParameters;
import org.junit.runners.parameterized.ParametersRunnerFactory;
import org.junit.runners.parameterized.TestWithParameters;

import java.util.Arrays;

@RunWith(Parameterized.class)
@Parameterized.UseParametersRunnerFactory(CustomParameterizedTest.RunnerFactory.class)
public class CustomParameterizedTest {

  @Parameterized.Parameters
  public static Iterable<Integer> data() {
    return Arrays.asList(new Integer[]{1, 2, 3});
  }

  private int i;

  public CustomParameterizedTest(int i) {
    this.i = i;
  }

  @Test
  public void test() {
    System.out.println(i);
  }

  public static class RunnerFactory implements ParametersRunnerFactory {
    @Override
    public org.junit.runner.Runner createRunnerForTestWithParameters(TestWithParameters test) throws InitializationError {
      return new A(test);
    }
  }

  public static class A extends BlockJUnit4ClassRunnerWithParameters {
    private final Object[] parameters;

    public A(TestWithParameters test) throws InitializationError {
      super(test);
      parameters = test.getParameters().toArray(new Object[test.getParameters().size()]);
    }

    @Override
    public Object createTest() throws Exception {
      return getTestClass().getOnlyConstructor().newInstance(parameters);
    }
  }
}

Based on the Javadocs in the JUnit Parameterized class, this is how they expect you to create a custom test runner that supports parameterization.

UPDATE

Updated to name the custom runner A