### Question:
ValueExtractors { public static ValueExtractor fromQueryParameter(final String parameter) { return new QueryValueExtractor(parameter); } private  ValueExtractors(); static ValueExtractor createValueExtractor(final ExtractorSource source,
                                                      final String sourceKey); static ValueExtractor fromQueryParameter(final String parameter); static ValueExtractor fromHttpHeader(final String headerName); static ValueExtractor chain(final List<ValueExtractor> extractors); static ValueExtractor chain(final ValueExtractor... extractors);  }### Answer:
@Test public void testQueryExtractor() throws Exception { final MockHttpServletRequest request = new MockHttpServletRequest(); final ValueExtractor countryExtractor = ValueExtractors.fromQueryParameter("country"); Assert.assertNull("Request missing parameter should return null", countryExtractor.extract(request)); request.setParameter("country", "US"); Assert.assertEquals("US", countryExtractor.extract(request)); }