RetrofitBug.java

import okhttp3.ResponseBody;
import okhttp3.mockwebserver.MockResponse;
import okhttp3.mockwebserver.MockWebServer;
import okhttp3.mockwebserver.RecordedRequest;
import org.junit.Rule;
import org.junit.Test;
import retrofit2.Call;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.http.GET;
import retrofit2.http.Headers;
import retrofit2.http.Query;

import static org.junit.Assert.assertEquals;

public final class RetrofitBug {
  @Rule public final MockWebServer server = new MockWebServer();

  interface Service {
    @GET("/path")
    @Headers("User-Agent: Test Case")
    Call<ResponseBody> search(@Query("keyword") String keyword);
  }

  @Test public void test() throws Exception {
    Retrofit retrofit = new Retrofit.Builder()
        .baseUrl(server.url("/"))
        .build();
    Service example = retrofit.create(Service.class);

    server.enqueue(new MockResponse()
        .addHeader("Content-Type", "text/plain")
        .setBody("Hi"));

    Call<ResponseBody> call = example.search("hello");
    Response<ResponseBody> response = call.execute();
    assertEquals("text/plain", response.headers().get("Content-Type"));
    assertEquals("Hi", response.body().string());

    RecordedRequest recordedRequest = server.takeRequest();
    assertEquals("/path?keyword=hello", recordedRequest.getPath());
    assertEquals("Test Case", recordedRequest.getHeader("User-Agent"));
  }
}