### Question:
LambdaServer implements HttpServer { @Override public HttpServer listen() { processRequest(); return this; } LambdaServer(Vertx vertx, Context context, InputStream input, OutputStream output); @Override boolean isMetricsEnabled(); @Override ReadStream<HttpServerRequest> requestStream(); @Override HttpServer requestHandler(Handler<HttpServerRequest> handler); @Override Handler<HttpServerRequest> requestHandler(); @Override HttpServer connectionHandler(Handler<HttpConnection> handler); @Override ReadStream<ServerWebSocket> websocketStream(); @Override HttpServer websocketHandler(Handler<ServerWebSocket> handler); @Override Handler<ServerWebSocket> websocketHandler(); @Override HttpServer listen(); @Override HttpServer listen(int port, String host); @Override HttpServer listen(int port, String host, Handler<AsyncResult<HttpServer>> listenHandler); @Override HttpServer listen(int port); @Override HttpServer listen(int port, Handler<AsyncResult<HttpServer>> listenHandler); @Override HttpServer listen(Handler<AsyncResult<HttpServer>> listenHandler); @Override void close(); @Override void close(Handler<AsyncResult<Void>> completionHandler); @Override int actualPort();  }### Answer:
@Test public void testListen(TestContext context) { server.requestHandler(req -> { context.assertEquals("0.0.0.0", req.host()); req.response().end("data"); }); context.assertEquals(server, server.listen()); context.assertEquals(0, server.actualPort()); JsonObject response = new JsonObject(outputData.toString()); context.assertEquals("4", response.getJsonObject("headers").getString("Content-Length")); context.assertEquals(200, response.getInteger("statusCode")); context.assertTrue(response.getBoolean("isBase64Encoded")); context.assertEquals("data", new String(response.getBinary("body"))); }