Mockito JUnit Testing POST files

Question

I am struggling to write test(s) for the following post method (junit/mockito)

POST method

public JSONObject post(final String url, final Map<String, File> fileMap) {

    final OkHttpClient client = OkHttpClientSingleton.getInstance();
    final MultipartBody.Builder builder = new MultipartBody.Builder()
            .setType(MultipartBody.FORM);

    try {
        for (final Map.Entry entry : fileMap.entrySet()) {
            final String contentType;
            final Path path = Paths.get(((File) entry.getValue()).getAbsolutePath());
            contentType = Files.probeContentType(path);
            final MediaType FILE_MEDIA_TYPE = MediaType.parse(contentType);
            builder.addFormDataPart((String) entry.getKey(), ((File) entry.getValue()).getName(), RequestBody.create(FILE_MEDIA_TYPE, (File) entry.getValue()));

        }
    } catch (final IOException e) {
        e.printStackTrace();
        return null;
    }

    final RequestBody requestBody = builder.build();
    final Request request = new Request.Builder()
            .url(url)
            .post(requestBody)
            .build();

    return execute(client, request);

}

and the execute method looks like:

private JSONObject execute(final OkHttpClient client, final Request request) {
    try {
        final Response response = client.newCall(request).execute();
        final String str = Objects.requireNonNull(response.body()).string();
        return new JSONObject(str);
    } catch (final IOException e) {
        e.printStackTrace();
    }
    return buildErrorResponse("Unable to execute request");
}

I have no "fields" to create mocks for (my usual MO!), any tips muchappreciated. I can force an error easily enough but to test full flow at least until the POST

Answer 1

You can mock the web application that receives the post and verify that the correct data is send. Eg you can use http://mock-server.com for this.