Mocking HttpURLConnection

gistfile1.java

public class URLRequestUnit extends InstrumentationTestCase
{
    private static final String API_URL =
            "http://www.example.com/api/users";

    public void testHttpOkay() throws Exception {
        MockURLStreamHandler handler = new MockURLStreamHandler();
        URL.setURLStreamHandlerFactory(handler);

        UsersRequest request = new UsersRequest();
        List<Users> users = request.doRequest();

        // Assert connection is set up correctly
        MockHttpURLConnection conn = handler.getConnection();
        assertEquals(API_URL, conn.getURL().toString());
        assertEquals("application/json", conn.getRequestProperty("Accept"));
        // etc...

        // Assert results are parsed correctly
        assertEquals(3, users.size());
        // etc...
    }

    public class MockURLStreamHandler extends URLStreamHandler
        implements
            URLStreamHandlerFactory
    {
        private MockHttpURLConnection mConnection;

        public MockHttpURLConnection getConnection() {
            return mConnection;
        }

        // *** URLStreamHandler

        @Override
        protected URLConnection openConnection(URL u) throws IOException {
            mConnection = new MockHttpURLConnection(u);
            return mConnection;
        }

        // *** URLStreamHandlerFactory

        @Override
        public URLStreamHandler createURLStreamHandler(String protocol) {
            return this;
        }

    }

    public class MockHttpURLConnection extends HttpURLConnection
    {

        protected MockHttpURLConnection(URL url) {
            super(url);
        }

        // *** HttpURLConnection

        @Override
        public InputStream getInputStream() throws IOException {
            // Load file in res/raw/users.json of the test project
            Resources res = getInstrumentation().getContext().getResources();
            return res.openRawResource(R.raw.users);
        }

        @Override
        public void connect() throws IOException {
        }

        @Override
        public void disconnect() {
        }

        @Override
        public boolean usingProxy() {
            return false;
        }

    }

}