Example Code - Java

To setup an expectation that responds to a request:

new MockServerClient("127.0.0.1", 1080)
        .when(
                request()
                        .withMethod("POST")
                        .withPath("/login")
                        .withQueryStringParameters(
                                new Parameter("returnUrl", "/account")
                        )
                        .withCookies(
                                new Cookie("sessionId", "2By8LOhBmaW5nZXJwcmludCIlMDAzMW")
                        )
                        .withBody(exact("{username: 'foo', password: 'bar'}")),
                exactly(1)
        )
        .respond(
                response()
                        .withStatusCode(401)
                        .withHeaders(
                                new Header("Content-Type", "application/json; charset=utf-8"),
                                new Header("Cache-Control", "public, max-age=86400")
                        )
                        .withBody("{ message: 'incorrect username and password combination' }")
                        .withDelay(new Delay(SECONDS, 1))
        );

To setup an expectation that forwards to a request:

new MockServerClient("127.0.0.1", 1080)
        .when(
                request()
                        .withMethod("GET")
                        .withPath("/index.html"),
                exactly(1)
        )
        .forward(
                forward()
                        .withHost("www.mock-server.com")
                        .withPort(80)
                        .withScheme(HTTP)
        );

To start a local instance of MockServer and setup an expectation that executes a callback:

MockServerClient mockServer = startClientAndServer(1080);

mockServer
        .when(
                request()
                        .withPath("/callback")
        )
        .callback(
                callback()
                        .withCallbackClass("org.mockserver.server.PrecannedTestExpectationCallback")
        );

and the callback class could be as follows:

public class PrecannedTestExpectationCallback implements ExpectationCallback {

    public static HttpResponse httpResponse = response()
            .withStatusCode(ACCEPTED_202.code())
            .withHeaders(
                    header("x-callback", "test_callback_header"),
                    header("Content-Length", "a_callback_response".getBytes().length),
                    header("Connection", "keep-alive")
            )
            .withBody("a_callback_response");

    @Override
    public HttpResponse handle(HttpRequest httpRequest) {
        if (httpRequest.getPath().getValue().endsWith("/callback")) {
            return httpResponse;
        } else {
            return notFoundResponse();
        }
    }
}

Note: these examples require the use of these static imports as follows:

The mockserver-example project contains multiple examples such as BookPageIntegrationTest that demonstrates a fully working examples.