title: trying to test with MocWebSerevr it got error
body: <p>Anyone knows what the error means?  Or maybe miss something?</p>
  
  <p>Was trying to start from this <a href="https://github.com/dherges/ok-testing/tree/v0.1.0/src" rel="nofollow noreferrer">sample</a>, </p>
  
  <p>added the dependency: <code>testImplementation 'com.squareup.okhttp3:mockwebserver:3.11.0'</code></p>
  
  <p>code was just added a @Test <code>findMessage_receivesAScriptedResponseFromMockBackend</code> to the AndroidStudio's sample unit test:</p>
  
  <pre><code>    public class ExampleUnitTest {
          @Test
          public void addition_isCorrect() {
              assertEquals(4, 2 + 2);
          }
  
      ///
      @Rule
      public MockWebServer mockBackend = new MockWebServer();
  
      private MessagesApi mockApi() {
          return new MessagesApi.Builder()
                  .baseUrl(mockBackend.url("/").toString())
                  .build();
      }
  
      @Test
      public void builder_returnsInstance() {
          final MessagesApi messagesApi = new MessagesApi.Builder()
                  .baseUrl("http://localhost:8888")
                  .build();
  
          assertNotNull(messagesApi);
      }
  
  @Test
  public void findMessage_receivesAScriptedResponseFromMockBackend() throws IOException {
      mockBackend.enqueue(
              new MockResponse()
                      .setBody("{\"text\":\"hello!\"}")
                      .setResponseCode(200)
                      .addHeader("Content-Type", "application/json;charset=utf-8")
      );
  
      final Response&lt;Message&gt; response = mockApi().findMessage("123").execute();
  
      assertTrue((response.code()) == (200));
      assertTrue((response.headers().get("Content-Type")).contains("application/json"));
  
      final ResponseBody rawResponseBody = response.raw().body();
      assertTrue((rawResponseBody.contentType().type()).equals("application"));
      assertTrue((rawResponseBody.contentType().subtype()).equals("json"));
  }
  
  public class Message {
  
      public String text;
  }
  
  public interface MessagesApi {
  
      @GET("/message")
      Call&lt;Message&gt; findMessage(@Query("query") String keyword);
  
  
      /** Convenient builder for MessagesApi */
      class Builder {
          private String baseUrl;
  
          public Builder() {}
  
          public Builder baseUrl(String baseUrl) {
              this.baseUrl = baseUrl;
  
              return this;
          }
  
          public MessagesApi build() {
              return new Retrofit.Builder()
                      .client(new OkHttpClient.Builder().build())
                      .addConverterFactory(GsonConverterFactory.create())
                      .baseUrl(baseUrl)
                      .build()
                      .create(MessagesApi.class);
          }
      }
  }
  }
  </code></pre>
  
  <p>When run the test it shows a error:</p>
  
  <pre><code>Oct 17, 2018 5:58:57 PM okhttp3.mockwebserver.MockWebServer$2 execute
  INFO: MockWebServer[60271] starting to accept connections
  Oct 17, 2018 5:58:57 PM okhttp3.mockwebserver.MockWebServer$2 acceptConnections
  INFO: MockWebServer[60271] done accepting connections: Socket closed
  Oct 17, 2018 5:58:57 PM okhttp3.mockwebserver.MockWebServer$2 execute
  INFO: MockWebServer[60272] starting to accept connections
  Exception in thread "MockWebServer" java.lang.NoSuchFieldError: H2_PRIOR_KNOWLEDGE
  at okhttp3.mockwebserver.MockWebServer$3.processConnection(MockWebServer.java:487)
  at okhttp3.mockwebserver.MockWebServer$3.execute(MockWebServer.java:442)
  at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
  at java.lang.Thread.run(Thread.java:745)
  Oct 17, 2018 5:59:07 PM okhttp3.mockwebserver.MockWebServer$2 acceptConnections
  INFO: MockWebServer[60272] done accepting connections: Socket closed
  
  java.net.SocketTimeoutException: timeout
  </code></pre>