### Question:
RestAuthLanguageCallbackHandler extends AbstractRestAuthCallbackHandler<LanguageCallback> { public LanguageCallback handle(HttpServletRequest request, HttpServletResponse response, JsonValue postBody, LanguageCallback originalCallback) { return originalCallback; }  LanguageCallback handle(HttpServletRequest request, HttpServletResponse response,
            JsonValue postBody, LanguageCallback originalCallback); String getCallbackClassName(); JsonValue convertToJson(LanguageCallback callback, int index); LanguageCallback convertFromJson(LanguageCallback callback, JsonValue jsonCallback);  }### Answer:
@Test public void shouldHandleCallback() { HttpServletRequest request = mock(HttpServletRequest.class); HttpServletResponse response = mock(HttpServletResponse.class); JsonValue jsonPostBody = mock(JsonValue.class); LanguageCallback originalLanguageCallback = mock(LanguageCallback.class); LanguageCallback languageCallback = restAuthLanguageCallbackHandler.handle(request, response, jsonPostBody, originalLanguageCallback); assertEquals(originalLanguageCallback, languageCallback); }