Test WebSocket behaviors

Use this to test the WebSocketBehavior of a page, or a WebSocketResource, in a unit test. WebSocketTester opens an emulated connection on top of a WicketTester, sends messages as the browser would, and hands you every message the server sends back.

Add the test dependency

pom.xml

<dependency>
    <groupId>org.apache.wicket</groupId>
    <artifactId>wicket-native-websocket-tester</artifactId>
    <version>${wicket.version}</version>
    <scope>test</scope>
</dependency>

The class is org.apache.wicket.protocol.ws.tester.WebSocketTester. It works with the WicketTester you already use; see Test pages and components.

Send a message and check the answer

Start the page, create a WebSocketTester for it, and override onOutMessage to collect what the server pushes:

ChatPageTest.java

class ChatPageTest {
    private WicketTester tester;

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

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

    @Test
    void echoesMessageInUpperCase() {
        ChatPage page = tester.startPage(ChatPage.class);
        List<String> received = new ArrayList<>();

        WebSocketTester webSocket = new WebSocketTester(tester, page) {
            @Override
            protected void onOutMessage(String message) {
                received.add(message);
            }
        };

        webSocket.sendMessage("hello");
        webSocket.destroy();

        assertEquals(List.of("HELLO"), received);
    }
}

sendMessage calls the behavior’s onMessage in the test thread, so by the time it returns the answers are in. Binary messages work the same way with sendMessage(byte[], offset, length) and the matching onOutMessage(byte[], int, int). destroy() closes the connection, which calls the behavior’s onClose.

When the behavior re-renders components with handler.add(...), the message you receive is the <ajax-response> XML. Check that it contains the markup you expect.

Test a push from the server

Push messages do not come from the browser. Broadcast one to the page’s connection, identified by the application, the session id and the page key:

webSocket.broadcast(tester.getApplication(), tester.getHttpSession().getId(),
    new PageIdKey(page.getPageId(), page.getClass().getName()), new JobProgress(50));

The PageIdKey takes the page class name as second argument, because the connection is registered with it. broadcastAll(application, message) reaches every connection. The page’s onEvent or the behavior’s onPush runs in the test thread, and its answer arrives in onOutMessage. WebSocketTester sets a same-thread executor for push messages, so nothing has to be awaited.

Test a WebSocketResource

For a shared WebSocketResource, pass its name instead of a page:

WebSocketTester webSocket = new WebSocketTester(tester, "prices") {
    @Override
    protected void onOutMessage(String message) {
        received.add(message);
    }
};

The resource must be registered in the application’s init() as in production. Push updates over a WebSocket shows the behavior and resource side.