Mock HttpResponse with Robolectric

Question

Using Robolectric 2.3-SNAPSHOT, I want to test an object that'll execute a request in the background. In order to isolate it, I'm trying to mock the HttpResponse returned, without success after some hours invested.

I've created a project that anyone can clone. Simly run ./gradlew check https://github.com/Maragues/RobolectricDummyProject (git clone https://github.com/Maragues/RobolectricDummyProject.git)

I've tried

• Robolectric.setDefaultHttpResponse(200, "my_mocked_word");

• MockWebServer (https://code.google.com/p/mockwebserver/)

But the tests fail because they query the real URL

  private static final String MOCKED_WORD = "MOCKED";

  @Test
  public void mockedRequestUsingMockServer() throws Exception {
    mMockWebServer.enqueue(new MockResponse().setBody(MOCKED_WORD));
    mMockWebServer.play();

    Robolectric.getFakeHttpLayer().interceptHttpRequests(false);
    Robolectric.getFakeHttpLayer().interceptResponseContent(false);

    String result = request.loadDataFromNetwork();

    assertEquals(MOCKED_WORD, result);
  }

  @Test
  public void mockedRequestUsingRobolectric() throws Exception {
    Robolectric.setDefaultHttpResponse(200, MOCKED_WORD);

    String result = request.loadDataFromNetwork();

    assertEquals(MOCKED_WORD, result);
  }

The code executing the request

public String loadDataFromNetwork() throws Exception {
    // With Uri.Builder class we can build our url is a safe manner
    Uri.Builder uriBuilder = Uri.parse("http://robospice-sample.appspot.com/reverse").buildUpon();
    uriBuilder.appendQueryParameter("word", word);

    String url = uriBuilder.build().toString();

    HttpURLConnection urlConnection = (HttpURLConnection) new URL(url)
      .openConnection();
    String result = IOUtils.toString(urlConnection.getInputStream());
    urlConnection.disconnect();

    return result;
  }

Possibly related questions

• Can't capture HTTP request with robolectric (I've tried that without success. Perhaps I'm missing something)
• Anyone had success mocking HttpRequests with Robolectric? (I'm not using eclipse)

Answer 1

You can try this(ref:https://github.com/square/okhttp/tree/master/mockwebserver).

  // Create a MockWebServer. These are lean enough that you can create a new
    // instance for every unit test.
    MockWebServer server = new MockWebServer();
    // Schedule some responses.
    server.enqueue(new MockResponse().setBody("it's all cool"));
    // Start the server.
    server.play();
    // Ask the server for its URL. You'll need this to make HTTP requests.
    //Http is my own http executor.
    Http.Response response = http.get(server.getUrl("/"));

then, you can compare the response to server.enqueue(new MockResponse().setBody("it's all cool"));

MockWebServer is a part of okhttp https://github.com/square/okhttp/tree/master/mockwebserver. the URLConnectionImpl in android 4.4 have been changed from defaultHttpClient to Okhttp.

Answer 2

You're disabling Roboelectric's HTTP layer, so you're using the real HTTP layer. This means that there's no clever magic happening under the hood of your test: when you send an HTTP request, it's really going out onto the internet (as you are seeing).

MockWebServer doesn't stop this. It just sets up a web server locally, that your test can connect to.

So to resolve this problem, you need to stop attempting to connect to a real server, and instead, connect to the mock server. To do this, yo need to inject/set the URL in the request.

@Test
  public void mockedRequestUsingMockServer() throws Exception {
    mMockWebServer = new MockWebServer();
    mMockWebServer.play();
    mMockWebServer.enqueue(new MockResponse().setResponseCode(200).setBody(MOCKED_WORD));

    request.myUrl = mMockWebServer.getUrl("/");

    String result = request.loadDataFromNetwork();

    assertEquals(MOCKED_WORD, result);
    mMockWebServer.shutdown();
  }

Answer 3

It turns out that Robolectric's FakeHttpLayer only works with Apache's HttpClient, which is highly discouraged on versions greater than Froyo. Extracted from Robolectric's Google Group

That being said, the usage of HttpUrlConnection will cause you trouble. I'd try to use Android's implementation of HttpClient where possible, since Robolectric intercepts all calls to that library and lets you set up canned responses to your HTTP calls. We're looking at doing the same for HttpUrlConnection, though it's not clear when that'll happen.

Apart from that, a unit test should not need to mock the HTTP layer. My approach was wrong from the beginning.