Getting java.lang.RuntimeException: Stub when testing with JSONObject in Robolectric

I am trying to test a method that parses a JSONObject. I am using Robolectric and am getting a java.lang.RuntimeException: Stub when doing so. The exception is thrown when trying to create the new JSONObject.

Why is it giving me this error? Does this have to do because I am accessing a static method?

@Test
public void parseGameJsonShouldReturnNotNullGame() throws Exception {
    JSONObject obj = new JSONObject("{" +
            "_id: \"538e72fe6a15ceec142a71c8\", " +
            "name: \"World of Warcraft\", " +
            "coverPhoto: [\"world_of_warcraft_pc.jpg\"], " +
            "platform: \"pc\", " +
            "genre: \"mmorpg\" " +
            "}");
    Game game = JsonManager.parseGameJson(obj);
    assertNotNull(game);
}

public static Game parseGameJson(JSONObject obj) {
    try {
        String id = "";
        if (obj.has(GlobalVars.KEY_ID)) {
            id = obj.getString(GlobalVars.KEY_ID);
        }

        String name = "";
        if (obj.has(GlobalVars.KEY_NAME)) {
            name = obj.getString(GlobalVars.KEY_NAME);
        }

        String genre = "";
        if (obj.has(GlobalVars.KEY_GENRE)) {
            genre = obj.getString(GlobalVars.KEY_GENRE);
        }

        String platform = "";
        if (obj.has(GlobalVars.KEY_PLATFORM)) {
            platform = obj.getString(GlobalVars.KEY_PLATFORM);
        }

        String coverPhoto = "";
        if (obj.has(GlobalVars.KEY_COVER_PHOTO)) {
            JSONArray coverPhotoArray = obj.getJSONArray(GlobalVars.KEY_COVER_PHOTO);

            for (int c = 0; c < coverPhotoArray.length(); c++) {
                if (c == 0) {
                    coverPhoto = coverPhotoArray.getString(c);
                }
                else {
                    coverPhoto = coverPhoto + ", " + coverPhotoArray.getString(c);
                }
            }
        }

        return new Game(id, name, genre, platform, coverPhoto);
    }
    catch (JSONException e) { e.printStackTrace(); }

    return null;
}