public void NullExpressionWillBeTreatedAsEmptyExpression() { var instance = new NullExpressionTest { Text = "hi" }; var result = this.provider.Validate(instance); result.Should().NotBeNull("because we should always get a result"); result.IsApplicable.Should().BeTrue("because a regular expression attribute applies to a string property"); result.IsSuccess.Should().BeTrue("because a null regular expression does not use any regular expressions"); }