@Test
 public void valueWithClassifiers() {
   String result = configuration.getOptionalString("propertyWithClassifiers", "a", "b");
   assertEquals("value", result);
 }
 @Test
 public void nullWhenEmpty() {
   String result = configuration.getOptionalString("empty");
   assertNull(result);
 }
 @Test
 public void valueIsTrimmed() {
   String result = configuration.getOptionalString("propertyWithSpaces");
   assertEquals("value", result);
 }
 @Test
 public void nullWhenNotFound() {
   String result = configuration.getOptionalString("xxx");
   assertNull(result);
 }
 @Test
 public void found() {
   String result = configuration.getOptionalString("stringProperty");
   assertEquals("stringValue", result);
 }