Test a page with WicketTester

In this tutorial you write tests for the application you built in the previous tutorials. The tests render the home page, click its links, submit the guestbook form and check what Ajax redraws. They run in JUnit, without a browser and without starting a server.

Start from the myapp project as you left it at the end of Update a page with Ajax. The quickstart already put the test dependencies in pom.xml: wicket-tester and JUnit.

1. Run the test you already have

The quickstart generated TestHomePage.java in src/test/java/com/example:

public class TestHomePage {
    private WicketTester tester;

    @BeforeEach
    public void setUp() {
        tester = new WicketTester(new WicketApplication());
    }

    @Test
    public void homepageRendersSuccessfully() {
        tester.startPage(HomePage.class);
        tester.assertRenderedPage(HomePage.class);
    }
}

WicketTester runs your application in memory, with a fake request, response and session. startPage renders a page the way a browser request would. assertRenderedPage checks which page came out.

Run the tests from the project folder:

mvn test

Maven reports Tests run: 1, Failures: 0. The test still passes after all your changes, so the home page, the base page and both panels render without errors. A test like this catches a wicket:id in the HTML without a component in Java, and the other way around.

2. Check what a label shows

Add a test to TestHomePage that checks the greeting:

@Test
public void greetsTheVisitor() {
    tester.startPage(HomePage.class);
    tester.assertLabel("greeting", "Hello, Wicket!");
}

The first argument is the path of the component: its id, prefixed with the ids of the containers it sits in, separated by colons. The greeting is added straight to the page, so its path is its id.

Run mvn test. Two tests pass. Change the expected text to Hello! and run again: the test fails and tells you what the label showed instead. Change it back.

3. Click the Ajax counter

clickLink clicks a link. For an AjaxLink it sends an Ajax request, as the browser would. Add:

@Test
public void countsClicks() {
    tester.startPage(HomePage.class);
    tester.assertLabel("clicks", "0");

    tester.clickLink("count");

    tester.assertLabel("clicks", "1");
    tester.assertComponentOnAjaxResponse("clicks");
}

assertComponentOnAjaxResponse checks that the label was part of the Ajax response, so the browser would have redrawn it. Run mvn test: three tests pass.

4. Follow a link to another page

The links in the header sit inside the HeaderPanel, which has the id header. Their paths start with that id:

@Test
public void navigatesToTheAboutPage() {
    tester.startPage(HomePage.class);

    tester.clickLink("header:about");

    tester.assertRenderedPage(AboutPage.class);
}

Run mvn test: four tests pass.

5. Test that the form opens

The guestbook form is hidden until the visitor clicks “Write a message”. Create TestGuestbookPage.java in src/test/java/com/example, and test that link first. Keep the application in a field, so later tests can look at its guestbook:

package com.example;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.apache.wicket.util.tester.FormTester;
import org.apache.wicket.util.tester.WicketTester;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

public class TestGuestbookPage {
    private WicketApplication application;
    private WicketTester tester;

    @BeforeEach
    public void setUp() {
        application = new WicketApplication();
        tester = new WicketTester(application);
    }

    @AfterEach
    public void tearDown() {
        tester.destroy();
    }

    @Test
    public void opensTheForm() {
        tester.startPage(GuestbookPage.class);
        tester.assertInvisible("form");

        tester.clickLink("write");

        tester.assertVisible("form");
        tester.assertInvisible("write");
        tester.assertComponentOnAjaxResponse("form");
    }
}

Each test gets a new application and so a new guestbook, and destroy() cleans up after each test. assertInvisible and assertVisible check the visibility that onConfigure() decided.

Run mvn test: five tests pass.

6. Test that the guestbook rejects empty input

newFormTester gives you a FormTester for the form at that path. Its submit() sends the form with the fields as they are. Add a test that submits the form empty:

@Test
public void requiresNameAndMessage() {
    tester.startPage(GuestbookPage.class);
    tester.clickLink("write");

    FormTester form = tester.newFormTester("form");
    form.submit();

    tester.assertErrorMessages("'Name' is required.", "'Message' is required.");
    assertEquals(1, application.getGuestbook().getEntries().size());
}

assertErrorMessages checks the error messages the submit produced. The guestbook still holds only its welcome entry.

Run mvn test: six tests pass.

7. Test that the guestbook saves an entry

setValue fills in a field. Its first argument is the path of the field relative to the form. Add:

@Test
public void savesAnEntry() {
    tester.startPage(GuestbookPage.class);
    tester.clickLink("write");

    FormTester form = tester.newFormTester("form");
    form.setValue("name", "Ann");
    form.setValue("text", "Nice site!");
    form.submit();

    tester.assertNoErrorMessage();
    tester.assertInfoMessages("Thanks for signing, Ann!");
    assertEquals("Ann", application.getGuestbook().getEntries().get(0).getName());
}

Run mvn test: seven tests pass.

8. Submit through the Ajax button

form.submit() submits the form as a plain request. To test the Ajax button, fill in the fields and fire the button’s click event with executeAjaxEvent. Wicket then submits the form over Ajax, as the browser does:

@Test
public void savesAnEntryWithAjax() {
    tester.startPage(GuestbookPage.class);
    tester.clickLink("write");

    FormTester form = tester.newFormTester("form");
    form.setValue("name", "Bob");
    form.setValue("text", "Hello from Ajax.");
    tester.executeAjaxEvent("form:save", "click");

    tester.assertComponentOnAjaxResponse("entries");
    tester.assertComponentOnAjaxResponse("feedback");
    assertEquals("Bob", application.getGuestbook().getEntries().get(0).getName());
}

Run mvn test: eight tests pass.

9. Fire the timer

A test does not wait ten seconds for the timer. executeAllTimerBehaviors fires every timer on a page at once. Add an entry to the guestbook behind the page’s back, as another visitor would, and fire the timers:

@Test
public void refreshesTheList() {
    tester.startPage(GuestbookPage.class);
    application.getGuestbook().add(new Entry("Cid", "Signed in another browser."));

    tester.executeAllTimerBehaviors(tester.getLastRenderedPage());

    tester.assertComponentOnAjaxResponse("entries");
    tester.assertContains("Signed in another browser.");
}

assertContains searches the last response, here the Ajax response with the redrawn list.

Run mvn test: all nine tests pass. Together they cover every page, the counter, the navigation, the hidden form, both ways of submitting the guestbook and the timer, and none of them needs a browser or a server.

Continue from here

This is the last of the tutorials. From here, the how-to guides help you with a specific goal: start with Test pages and components and Test forms for more of what you used here, and WicketTester lists its methods. Best practices explains how to keep a growing Wicket application easy to change and to test.