Android Unit Test Utility Classes

README.md

Android/Java Unit Test Utility Classes

RetrofitTestUtil

Mocks Retrofit Calls (success/failure)

e.g.

    RetrofitTestUtil.createCall(createDummyResponse());
    RetrofitTestUtil.createCall(500, createDummyErrorResponse());

JsonTestUtil

Converts JSON files into JSON objects using Jackson

e.g.

    ApiModel model = JsonTestUtil.getJsonFromFile("model.json", ApiModel.class);

Samples

    // Mock a successful API call
    ApiModel model = JsonTestUtil.getJsonFromFile("model.json", ApiModel.class);
    Mockito.when(apiService.get())
            .thenReturn(RetrofitTestUtil.createCall(actors));

JsonTestUtil.java

public class JsonTestUtil {
    private static ObjectMapper mObjectMapper;

    private static ObjectMapper getObjectMapper() {
        if (mObjectMapper == null) {
            mObjectMapper = new ObjectMapper();
        }

        return mObjectMapper;
    }

    @JsonIgnore
    public static <M> M fromString(String jsonString, Class<M> modelClass) throws IOException {
        return getObjectMapper().readValue(jsonString, modelClass);
    }

    @JsonIgnore
    public static String fromJson(Object object) throws JsonProcessingException {
        return getObjectMapper().writeValueAsString(object);
    }

    public static <M> M getJsonFromFile(String jsonFileName, Class<M> jsonClass) {
        InputStream inputStream = getInputStreamFromFile(jsonFileName);
        String jsonString = convertStreamToString(inputStream);
        M jsonObject = null;

        try {
            jsonObject = fromString(jsonString, jsonClass);
        } catch (IOException e) {
            e.printStackTrace();
        }

        return jsonObject;
    }

    private static InputStream getInputStreamFromFile(String fileName) {
        ClassLoader classLoader = ClassLoader.getSystemClassLoader();
        return classLoader.getResourceAsStream(fileName);
    }

    private static String convertStreamToString(java.io.InputStream is) {
        java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A");
        return s.hasNext() ? s.next() : "";
    }

}

RetrofitTestUtil.java

public class RetrofitTestUtil {

    public static <T> Call<T> createCall(T response) {
        return new MockCall<>(response);
    }

    public static <T> Call<T> createCall(int responseCode, T response) {
        return new MockCall<>(responseCode, response);
    }

    private static class MockCall<T> implements Call<T> {

        final T mResponse;

        final int mCode;

        public MockCall(int code, T response) {
            mResponse = response;
            mCode = code;
        }

        public MockCall(T response) {
            this(200, response);
        }

        @Override
        public Response<T> execute() throws IOException {
            return buildResponse();
        }

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

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

        @Override
        public Request request() {
            return null;
        }

        @NonNull
        private Response<T> buildResponse() {
            if (mCode > 199 && mCode < 300) {
                return Response.success(mResponse);
            } else {
                return Response.error(mCode, new DummyResponseBody());
            }
        }

        @Override
        public void enqueue(Callback<T> callback) {
            if (mCode > 0) {
                callback.onResponse(null, buildResponse());
            } else {
                callback.onFailure(null, null);
            }
        }

        @Override
        public void cancel() {

        }

        @SuppressWarnings("CloneDoesntCallSuperClone")
        @Override
        public Call<T> clone() {
            return new MockCall<>(mResponse);
        }
    }

    private static class DummyResponseBody extends ResponseBody {
        @Override
        public MediaType contentType() {
            return null;
        }

        @Override
        public long contentLength() {
            return 0;
        }

        @Override
        public BufferedSource source() {
            return null;
        }
    }

}