Java – ParameterizedTest with a name in Eclipse Testrunner

I think there's nothing built in in jUnit 4 to do this.

I've implemented a solution. I've built my own Parameterized class based on the existing one:

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

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

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

    // TODO: single-class this extension

    private static class TestClassRunnerForParameters extends TestClassMethodsRunner {
        private final Object[] fParameters;

        private final Class<?> fTestClass;

        private Object instance;

        private final int fParameterSetNumber;

        private final Constructor<?> fConstructor;

        private TestClassRunnerForParameters(Class<?> klass, Object[] parameters, int i) throws Exception {
            super(klass);
            fTestClass = klass;
            fParameters = parameters;
            fParameterSetNumber = i;
            fConstructor = getOnlyConstructor();
            instance = fConstructor.newInstance(fParameters);
        }

        @Override
        protected Object createTest() throws Exception {
            return instance;
        }

        @Override
        protected String getName() {
            String name = null;
            try {
                Method m = getNameMethod();
                if (m != null)
                    name = (String) m.invoke(instance);
            } catch (Exception e) {
            }
            return String.format("[%s]", (name == null ? fParameterSetNumber : name));
        }

        @Override
        protected String testName(final Method method) {
            String name = null;
            try {
                Method m = getNameMethod();
                if (m != null)
                    name = (String) m.invoke(instance);
            } catch (Exception e) {
            }
            return String.format("%s[%s]", method.getName(), (name == null ? fParameterSetNumber : name));
        }

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

        private Method getNameMethod() throws Exception {
            for (Method each : fTestClass.getMethods()) {
                if (Modifier.isPublic((each.getModifiers()))) {
                    Annotation[] annotations = each.getAnnotations();
                    for (Annotation annotation : annotations) {
                        if (annotation.annotationType() == Name.class) {
                            if (each.getReturnType().equals(String.class))
                                return each;
                            else
                                throw new Exception("Name annotated method doesn't return an object of type String.");
                        }
                    }
                }
            }
            return null;
        }
    }

    // TODO: I think this now eagerly reads parameters, which was never the
    // point.

    public static class RunAllParameterMethods extends CompositeRunner {
        private final Class<?> fKlass;

        public RunAllParameterMethods(Class<?> klass) throws Exception {
            super(klass.getName());
            fKlass = klass;
            int i = 0;
            for (final Object each : getParametersList()) {
                if (each instanceof Object[])
                    super.add(new TestClassRunnerForParameters(klass, (Object[]) each, i++));
                else
                    throw new Exception(String.format("%s.%s() must return a Collection of arrays.", fKlass.getName(), getParametersMethod().getName()));
            }
        }

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

        private Method getParametersMethod() throws Exception {
            for (Method each : fKlass.getMethods()) {
                if (Modifier.isStatic(each.getModifiers())) {
                    Annotation[] annotations = each.getAnnotations();
                    for (Annotation annotation : annotations) {
                        if (annotation.annotationType() == Parameters.class)
                            return each;
                    }
                }
            }
            throw new Exception("No public static parameters method on class " + getName());
        }
    }

    public MyParameterized(final Class<?> klass) throws Exception {
        super(klass, new RunAllParameterMethods(klass));
    }

    @Override
    protected void validate(MethodValidator methodValidator) {
        methodValidator.validateStaticMethods();
        methodValidator.validateInstanceMethods();
    }

}

To be used like:

@RunWith(MyParameterized.class)
public class ParameterizedTest {
    private File file;
    public ParameterizedTest(File file) {
        this.file = file;
    }

    @Test
    public void test1() throws Exception {}

    @Test
    public void test2() throws Exception {}

    @Name
    public String getName() {
        return "coolFile:" + file.getName();
    }

    @Parameters
    public static Collection<Object[]> data() {
        // load the files as you want
        Object[] fileArg1 = new Object[] { new File("path1") };
        Object[] fileArg2 = new Object[] { new File("path2") };

        Collection<Object[]> data = new ArrayList<Object[]>();
        data.add(fileArg1);
        data.add(fileArg2);
        return data;
    }
}

This implies that I instantiate the test class earlier. I hope this won't cause any errors ... I guess I should test the tests :)