LabelledParameterized.java

/**
 * From http://stackoverflow.com/questions/650894/change-test-name-of-parameterized-tests/2052202#2052202
 * Licence: GPLv3
 * Version: r3789 (Jan 2010)
 */

package uk.ac.lkl.common.util.testing;

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.junit.runner.Description;
import org.junit.runners.Parameterized;

public class LabelledParameterized extends Parameterized {

    private List<String> labels;

    private Description labelledDescription;

    public LabelledParameterized(Class<?> cl) throws Throwable {
	super(cl);
	initialiseLabels();
	generateLabelledDescription();
    }

    private void initialiseLabels() throws Exception {
	Collection<Object[]> parameterArrays = getParameterArrays();
	labels = new ArrayList<String>();
	for (Object[] parameterArray : parameterArrays) {
	    String label = parameterArray[0].toString();
	    labels.add(label);
	}

    }

    private Collection<Object[]> getParameterArrays() throws Exception {
	Method testClassMethod = getDeclaredMethod(this.getClass(),
		"getTestClass");
	Class<?> returnType = testClassMethod.getReturnType();
	if (returnType == Class.class)
	    return getParameterArrays4_3();
	else
	    return getParameterArrays4_4();
    }

    private Collection<Object[]> getParameterArrays4_3() throws Exception {
	Object[][] methodCalls = new Object[][] { new Object[] { "getTestClass" } };
	Class<?> cl = invokeMethodChain(this, methodCalls);
	Method[] methods = cl.getMethods();

	Method parametersMethod = null;
	for (Method method : methods) {
	    boolean providesParameters = method
		    .isAnnotationPresent(Parameters.class);
	    if (!providesParameters)
		continue;

	    if (parametersMethod != null)
		throw new Exception(
			"Only one method should be annotated with @Labels");

	    parametersMethod = method;
	}

	if (parametersMethod == null)
	    throw new Exception("No @Parameters method found");

	Collection<Object[]> parameterArrays = (Collection<Object[]>) parametersMethod
		.invoke(null);
	return parameterArrays;

    }

    private Collection<Object[]> getParameterArrays4_4() throws Exception {
	Object[][] methodCalls = new Object[][] {
		new Object[] { "getTestClass" },
		new Object[] { "getAnnotatedMethods", Class.class,
			Parameters.class },
		new Object[] { "get", int.class, 0 },
		// use array type for varargs (equivalent (almost))
		new Object[] { "invokeExplosively", Object.class, null,
			Object[].class, new Object[] {} } };
	Collection<Object[]> parameterArrays = invokeMethodChain(this,
		methodCalls);
	return parameterArrays;
    }

    private <T> T invokeMethodChain(Object object, Object[][] methodCalls)
	    throws Exception {
	for (Object[] methodCall : methodCalls) {
	    String methodName = (String) methodCall[0];
	    int parameterCount = (methodCall.length - 1) / 2;
	    Class<?>[] classes = new Class<?>[parameterCount];
	    Object[] arguments = new Object[parameterCount];
	    for (int i = 1; i < methodCall.length; i += 2) {
		Class<?> cl = (Class<?>) methodCall[i];
		Object argument = methodCall[i + 1];
		int index = (i - 1) / 2; // messy!
		classes[index] = cl;
		arguments[index] = argument;
	    }
	    Method method = getDeclaredMethod(object.getClass(), methodName,
		    classes);
	    object = method.invoke(object, arguments);
	}
	return (T) object;
    }

    // iterates through super-classes until found. Throws NoSuchMethodException
    // if not
    private Method getDeclaredMethod(Class<?> cl, String methodName,
	    Class<?>... parameterTypes) throws NoSuchMethodException {
	do {
	    try {
		Method method = cl
			.getDeclaredMethod(methodName, parameterTypes);
		return method;
	    } catch (NoSuchMethodException e) {
		// do nothing - just fall through to the below
	    }
	    cl = cl.getSuperclass();
	} while (cl != null);
	throw new NoSuchMethodException("Method " + methodName
		+ "() not found in hierarchy");
    }

    private void generateLabelledDescription() throws Exception {
	Description originalDescription = super.getDescription();
	labelledDescription = Description
		.createSuiteDescription(originalDescription.getDisplayName());
	ArrayList<Description> childDescriptions = originalDescription
		.getChildren();
	int childCount = childDescriptions.size();
	if (childCount != labels.size())
	    throw new Exception(
		    "Number of labels and number of parameters must match.");

	for (int i = 0; i < childDescriptions.size(); i++) {
	    Description childDescription = childDescriptions.get(i);
	    String label = labels.get(i);
	    Description newDescription = Description
		    .createSuiteDescription(label);
	    ArrayList<Description> grandChildren = childDescription
		    .getChildren();
	    for (Description grandChild : grandChildren)
		newDescription.addChild(grandChild);
	    labelledDescription.addChild(newDescription);
	}
    }

    @Override
    public Description getDescription() {
	return labelledDescription;
    }

}