Change test name of parameterized tests?

Question

Is there a way to set my own custom test case name when using Parameterized tests in Junit4?

I'd like to change the default "[Test class].runTest[n]" to something meaningful...

Answer 1

Looking at JUnit 4.5, its runner clearly doesn't support that, as that logic is buried inside a private class inside the Paramaterized class. You could not use the JUnit Parameterized runner, and create your own instead which would understand the concept of names (which leads to the question of how you might set a name ...).

From a JUnit perspective, it would be nice if instead of (or in addition to) just passing an increment, they would pass the comma delimited arguments. TestNG does this. If the feature is important to you, you can comment on the yahoo mailing list referenced at www.junit.org.

Answer 2

You can create a method like

@Test
public void name() {
 Assert.assertEquals("", inboundFileName);
}

While I wouldn't use it all the time it would be useful to figure out exactly which test number 143 is.

Answer 3

I recently came across the same problem when using JUnit 4.3.1. I implemented a new class which extends Parameterized called LabelledParameterized. It has been tested using JUnit 4.3.1, 4.4 and 4.5. It reconstructs the Description instance using the String representation of the first argument of each parameter array from the @Parameters method. You can see the code for this at:

http://code.google.com/p/migen/source/browse/trunk/java/src/.../LabelledParameterized.java?r=3789

and an example of its use at:

http://code.google.com/p/migen/source/browse/trunk/java/src/.../ServerBuilderTest.java?r=3789

The test description formats nicely in Eclipse which is what I wanted since this makes failed tests a lot easier to find! I will probably further refine and document the classes over the next few days/weeks. Drop the '?' part of the URLs if you want the bleeding edge. :-)

To use it, all you have to do is copy that class (GPL v3), and change @RunWith(Parameterized.class) to @RunWith(LabelledParameterized.class) assuming the first element of your parameter list is a sensible label.

I don't know if any later releases of JUnit address this issue but even if they did, I can't update JUnit since all my co-developers would have to update too and we have higher priorities than re-tooling. Hence the work in the class to be compilable by multiple versions of JUnit.

---

Note: there is some reflection jiggery-pokery so that it runs across the different JUnit versions as listed above. The version specifically for JUnit 4.3.1 can be found here and, for JUnit 4.4 and 4.5, here.

Answer 4

I make extensive use of static import for Assert and friends, so it is easy for me to redefine assertion:

private <T> void assertThat(final T actual, final Matcher<T> expected) {
    Assert.assertThat(editThisToDisplaySomethingForYourDatum, actual, expected);
}

For example, you could add a "name" field to your test class, initialized in the constructor, and display that on test failure. Just pass it in as the first elements of your parameters array for each test. This also helps label the data:

public ExampleTest(final String testLabel, final int one, final int two) {
    this.testLabel = testLabel;
    // ...
}

@Parameters
public static Collection<Object[]> data() {
    return asList(new Object[][]{
        {"first test", 3, 4},
        {"second test", 5, 6}
    });
}

Answer 5

With Parameterized as a model, I wrote my own custom test runner / suite -- only took about half an hour. It's slightly different from darrenp's LabelledParameterized in that it lets you specify a name explicitly rather than relying on the first parameter's toString().

It also doesn't use arrays because I hate arrays. :)

public class PolySuite extends Suite {

  // //////////////////////////////
  // Public helper interfaces

  /**
   * Annotation for a method which returns a {@link Configuration}
   * to be injected into the test class constructor
   */
  @Retention(RetentionPolicy.RUNTIME)
  @Target(ElementType.METHOD)
  public static @interface Config {
  }

  public static interface Configuration {
    int size();
    Object getTestValue(int index);
    String getTestName(int index);
  }

  // //////////////////////////////
  // Fields

  private final List<Runner> runners;

  // //////////////////////////////
  // Constructor

  /**
   * Only called reflectively. Do not use programmatically.
   * @param c the test class
   * @throws Throwable if something bad happens
   */
  public PolySuite(Class<?> c) throws Throwable {
    super(c, Collections.<Runner>emptyList());
    TestClass testClass = getTestClass();
    Class<?> jTestClass = testClass.getJavaClass();
    Configuration configuration = getConfiguration(testClass);
    List<Runner> runners = new ArrayList<Runner>();
    for (int i = 0, size = configuration.size(); i < size; i++) {
      SingleRunner runner = new SingleRunner(jTestClass, configuration.getTestValue(i), configuration.getTestName(i));
      runners.add(runner);
    }
    this.runners = runners;
  }

  // //////////////////////////////
  // Overrides

  @Override
  protected List<Runner> getChildren() {
    return runners;
  }

  // //////////////////////////////
  // Private

  private Configuration getConfiguration(TestClass testClass) throws Throwable {
    return (Configuration) getConfigMethod(testClass).invokeExplosively(null);
  }

  private FrameworkMethod getConfigMethod(TestClass testClass) {
    List<FrameworkMethod> methods = testClass.getAnnotatedMethods(Config.class);
    if (methods.isEmpty()) {
      throw new IllegalStateException("@" + Config.class.getSimpleName() + " method not found");
    }
    if (methods.size() > 1) {
      throw new IllegalStateException("Too many @" + Config.class.getSimpleName() + " methods");
    }
    FrameworkMethod method = methods.get(0);
    int modifiers = method.getMethod().getModifiers();
    if (!(Modifier.isStatic(modifiers) && Modifier.isPublic(modifiers))) {
      throw new IllegalStateException("@" + Config.class.getSimpleName() + " method \"" + method.getName() + "\" must be public static");
    }
    return method;
  }

  // //////////////////////////////
  // Helper classes

  private static class SingleRunner extends BlockJUnit4ClassRunner {

    private final Object testVal;
    private final String testName;

    SingleRunner(Class<?> testClass, Object testVal, String testName) throws InitializationError {
      super(testClass);
      this.testVal = testVal;
      this.testName = testName;
    }

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

    @Override
    protected String getName() {
      return testName;
    }

    @Override
    protected String testName(FrameworkMethod method) {
      return testName + ": " + method.getName();
    }

    @Override
    protected void validateConstructor(List<Throwable> errors) {
      validateOnlyOneConstructor(errors);
    }

    @Override
    protected Statement classBlock(RunNotifier notifier) {
      return childrenInvoker(notifier);
    }
  }
}

And an example:

@RunWith(PolySuite.class)
public class PolySuiteExample {

  // //////////////////////////////
  // Fixture

  @Config
  public static Configuration getConfig() {
    return new Configuration() {
      @Override
      public int size() {
        return 10;
      }

      @Override
      public Integer getTestValue(int index) {
        return index * 2;
      }

      @Override
      public String getTestName(int index) {
        return "test" + index;
      }
    };
  }

  // //////////////////////////////
  // Fields

  private final int testVal;

  // //////////////////////////////
  // Constructor

  public PolySuiteExample(int testVal) {
    this.testVal = testVal;
  }

  // //////////////////////////////
  // Test

  @Ignore
  @Test
  public void odd() {
    assertFalse(testVal % 2 == 0);
  }

  @Test
  public void even() {
    assertTrue(testVal % 2 == 0);
  }

}