Changing names of parameterized tests

Question

Is there a way to set my own custom test case names when using parameterized tests in JUnit4?

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

Answer 1

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 2

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 3

None of it was working for me, so I got the source for Parameterized and modified it create a a new test runner. I didn't have to change much but IT WORKS!!!

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import org.junit.Assert;
import org.junit.internal.runners.ClassRoadie;
import org.junit.internal.runners.CompositeRunner;
import org.junit.internal.runners.InitializationError;
import org.junit.internal.runners.JUnit4ClassRunner;
import org.junit.internal.runners.MethodValidator;
import org.junit.internal.runners.TestClass;
import org.junit.runner.notification.RunNotifier;

public class LabelledParameterized extends CompositeRunner {
static class TestClassRunnerForParameters extends JUnit4ClassRunner {
    private final Object[] fParameters;

    private final String fParameterFirstValue;

    private final Constructor<?> fConstructor;

    TestClassRunnerForParameters(TestClass testClass, Object[] parameters, int i) throws InitializationError {
        super(testClass.getJavaClass()); // todo
        fParameters = parameters;
        if (parameters != null) {
            fParameterFirstValue = Arrays.asList(parameters).toString();
        } else {
            fParameterFirstValue = String.valueOf(i);
        }
        fConstructor = getOnlyConstructor();
    }

    @Override
    protected Object createTest() throws Exception {
        return fConstructor.newInstance(fParameters);
    }

    @Override
    protected String getName() {
        return String.format("%s", fParameterFirstValue);
    }

    @Override
    protected String testName(final Method method) {
        return String.format("%s%s", method.getName(), fParameterFirstValue);
    }

    private Constructor<?> getOnlyConstructor() {
        Constructor<?>[] constructors = getTestClass().getJavaClass().getConstructors();
        Assert.assertEquals(1, constructors.length);
        return constructors[0];
    }

    @Override
    protected void validate() throws InitializationError {
        // do nothing: validated before.
    }

    @Override
    public void run(RunNotifier notifier) {
        runMethods(notifier);
    }
}

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public static @interface Parameters {
}

private final TestClass fTestClass;

public LabelledParameterized(Class<?> klass) throws Exception {
    super(klass.getName());
    fTestClass = new TestClass(klass);

    MethodValidator methodValidator = new MethodValidator(fTestClass);
    methodValidator.validateStaticMethods();
    methodValidator.validateInstanceMethods();
    methodValidator.assertValid();

    int i = 0;
    for (final Object each : getParametersList()) {
        if (each instanceof Object[])
            add(new TestClassRunnerForParameters(fTestClass, (Object[]) each, i++));
        else
            throw new Exception(String.format("%s.%s() must return a Collection of arrays.", fTestClass.getName(), getParametersMethod().getName()));
    }
}

@Override
public void run(final RunNotifier notifier) {
    new ClassRoadie(notifier, fTestClass, getDescription(), new Runnable() {
        public void run() {
            runChildren(notifier);
        }
    }).runProtected();
}

private Collection<?> getParametersList() throws IllegalAccessException, InvocationTargetException, Exception {
    return (Collection<?>) getParametersMethod().invoke(null);
}

private Method getParametersMethod() throws Exception {
    List<Method> methods = fTestClass.getAnnotatedMethods(Parameters.class);
    for (Method each : methods) {
        int modifiers = each.getModifiers();
        if (Modifier.isStatic(modifiers) && Modifier.isPublic(modifiers))
            return each;
    }

    throw new Exception("No public static parameters method on class " + getName());
}

public static Collection<Object[]> eachOne(Object... params) {
    List<Object[]> results = new ArrayList<Object[]>();
    for (Object param : params)
        results.add(new Object[] { param });
    return results;
}
}

Answer 4

Looking at JUnit 4.5, its runner clearly doesn't support that, as that logic is buried inside a private class inside the Parameterized 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 5

A workaround would be to catch and nest all Throwables into a new Throwable with a custom message that contains all information about the parameters. The message would appear in the stack trace. This works whenever a test fails for all assertions, errors and exceptions as they are all subclasses of Throwable.

My code looks like this:

@RunWith(Parameterized.class)
public class ParameterizedTest {

    int parameter;

    public ParameterizedTest(int parameter) {
        super();
        this.parameter = parameter;
    }

    @Parameters
    public static Collection<Object[]> data() {
        return Arrays.asList(new Object[][] { {1}, {2} });
    }

    @Test
    public void test() throws Throwable {
        try {
            assertTrue(parameter%2==0);
        }
        catch(Throwable thrown) {
            throw new Throwable("parameter="+parameter, thrown);
        }
    }

}

The stack trace of the failed test is:

java.lang.Throwable: parameter=1
    at sample.ParameterizedTest.test(ParameterizedTest.java:34)
Caused by: java.lang.AssertionError
    at org.junit.Assert.fail(Assert.java:92)
    at org.junit.Assert.assertTrue(Assert.java:43)
    at org.junit.Assert.assertTrue(Assert.java:54)
    at sample.ParameterizedTest.test(ParameterizedTest.java:31)
    ... 31 more

Answer 6

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);
  }

}