Retrofit 2 ErrorUtils to replace RetrofitError from Retrofit 1

ErrorUtils.java

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import javax.net.ssl.HttpsURLConnection;

import retrofit2.Response;
import retrofit2.adapter.rxjava.HttpException;

public final class ErrorUtils {
    private static final String TAG = "ErrorUtils";
    private static final int HTTP_RATE_LIMIT = 429;

    private ErrorUtils() {
    }

    public static int getErrorMessage(Throwable throwable) {
        final String responseMessage = throwable != null ? throwable.getMessage() : "'throwable' is null";

        // IOExceptions, etc SocketTimeoutException, Conversion error
        if (throwable instanceof IOException) {
            Log.e(TAG, responseMessage, throwable);

            return "No Network!";
        }

        // Any HttpExceptions
        if (throwable instanceof HttpException) {
            final HttpException error = ((HttpException) throwable);
            final Response<?> response = error.response();
            final String url = error.response().raw().request().url().toString();
            final int responseCode = response != null ? error.code() : 0;

            if (responseCode == HttpsURLConnection.HTTP_INTERNAL_ERROR) {
                Log.e(TAG, responseMessage, error);

                return "Internal error.";
            } else if (responseCode == HttpsURLConnection.HTTP_CLIENT_TIMEOUT) {
                Log.e(TAG, responseMessage, error);

                return "Client time out.";
            } else if (responseCode == HTTP_RATE_LIMIT) {
                Log.e(TAG, responseMessage, error);

                return "Rate limited.";
            } else {
                Log.e(TAG, responseMessage, error);

                // If all else fails
                return "Error has occurred. Please try again.";
            }
        }

        // If all else fails
        return "Error has occurred. Please try again.";
    }
}

ErrorUtilsTest.java

import org.junit.Test;

import java.io.IOException;
import java.net.HttpURLConnection;

import okhttp3.ResponseBody;
import retrofit2.Response;
import retrofit2.adapter.rxjava.HttpException;

import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.Mockito.mock;

@SuppressWarnings({"unchecked", "ThrowableInstanceNeverThrown"})
public final class ErrorUtilsTest {
    @Test 
    public void testGetErrorMessageNullThrowable() {
        assertThat(ErrorUtils.getErrorMessage(null)).isEqualTo("Error has occurred. Please try again.");
    }

    @Test
    public void testGetErrorMessageThrowableReturnGenericMessage() {
        assertThat(ErrorUtils.getErrorMessage(new Throwable())).isEqualTo("Error has occurred. Please try again.");
    }

    @Test
    public void testGetErrorMessageGenericNetworkError() {
        assertThat(ErrorUtils.getErrorMessage(new IOException())).isEqualTo("No Network!");
    }

    @Test
    public void testGetErrorMessageGenericHttp500Error() {
        final ResponseBody body = mock(ResponseBody.class);
        final Response<String> response = Response.error(HttpURLConnection.HTTP_INTERNAL_ERROR, body);
        final HttpException exception = new HttpException(response);

        assertThat(ErrorUtils.getErrorMessage(exception)).isEqualTo("Internal error.");
    }

    @Test
    public void testGetErrorMessageGenericHttp408Error() {
        final ResponseBody body = mock(ResponseBody.class);
        final Response<String> response = Response.error(HttpURLConnection.HTTP_CLIENT_TIMEOUT, body);
        final HttpException exception = new HttpException(response);

        assertThat(ErrorUtils.getErrorMessage(exception)).isEqualTo("Client time out.");
    }

    @Test
    public void testGetErrorMessageGenericHttp429Error() {
        final ResponseBody body = mock(ResponseBody.class);
        final Response<String> response = Response.error(429, body);
        final HttpException exception = new HttpException(response);

        assertThat(ErrorUtils.getErrorMessage(exception)).isEqualTo("Rate limited.");
    }
}