### Question:
Preconditions { public static String checkNotNullOrEmpty(String argument, Object errorMessage) { return checkArgument(argument, isNotNullOrEmptyPredicate, errorMessage); }  static T checkArgument(T argument, Function<T, Boolean> predicate, Object errorMessage); static T checkNotNull(T argument); static String checkNotNullOrEmpty(String argument, Object errorMessage); static T checkNotNull(T argument, Object errorMessage);  }### Answer:
@Test public void should_check_null_empty_when_argument_is_valid(){ Preconditions.checkNotNullOrEmpty("index", "value cannot be null"); }