Automatically test your Wicket panel HTML markup

Automatically test your Wicket panel HTML markup

November 1, 2009 21:03 4 comments

Are you testing your HTML markup automatically yet? If your markup does not match the Java code, your Wicket panel does not work. It’s easy to get early feedback when your panels are broken: just unit test them!

In this blog post I describe a way of automatically verifying that the HTML markup of Wicket panels match the Java code. Scroll down to download the demo project!

Unit test

Unit testing Wicket panels with EclipseI created a JUnit test that you can add to your project to automatically test as much Wicket Panels as possible. Automatic testing works by resolving all panels on the Java class path and feeding them to the WicketTester. When a panel has invalid markup, the WicketTester will give an error: early feedback!

How does it work?

The Wicket panels that can automatically be tested should have a ‘default’ Wicket constructor, like this:

public DemoPanel(String id)

Resolving all panels is done with Spring 2.5’s ClassPathScanningCandidateComponentProvider (don’t you love those names! How can they stay below 120 characters per line?)

The ClassPathScanningCandidateComponentProvider is a component provider that scans the classpath from a base package. It then applies exclude and include filters to the resulting classes to find candidates.

Testing panels

    public void testAllWicketPanels() throws Exception {
        WicketTester wicketTester = new WicketTester(new WicketApplication());
    	ClassPathScanningCandidateComponentProvider provider = new ClassPathScanningCandidateComponentProvider(true);
        provider.addIncludeFilter(new AssignableTypeFilter(Panel.class));
        Set components = provider.findCandidateComponents("nl/stuq/demo");
        for (BeanDefinition component : components) {
            Class clazz = Class.forName(component.getBeanClassName());
            	testWicketPanel(wicketTester, clazz);
    private void testWicketPanel(WicketTester wicketTester, Class clazz) {
    private boolean hasDefaultConstructor(Class clazz) {
        for(Constructor constructor : clazz.getConstructors()){
            if(constructor.getParameterTypes().length == 1 &&
                return true;
        return false;

The test instantiates a new WicketTester. After that, the ClassPathScanningCandidateComponentProvider is created and configured to scan only for Panel classes in the nl.stuq.demo package and below.
After that, the found components are all checked. If they have a default constructor, the test is executed.

The boolean hasDefaultConstructor(clazz) method checks if the class has a constructor with only one String argument, the Wicket id.

Keep in mind

  • This is only for lazy people (good developers are lazy in some ways).
  • You need a dependency to Spring.
  • Only Panels with a certain constructor are tested.
  • Only instantiating the Panel is tested, so code coverage has no meaning for this test. Real testing is still needed.

Download demo project

The demo project is a Maven project based on the Wicket 1.4.3 quickstart that contains the test class and an example panel to be tested.
Download demo project.

Extract the zip file and run mvn test to run the tests. Then fire up your IDE and check how it’s done.

You can change or adapt the given JUnit test to also automatically test classes extending from Page or Component.

Join in with your opinions and code! I’m curious to see what clever way you have of testing code.