public void Ignore_DescriptorIsNull_ArgumentNullException()
        {
            // arrange
            // act
            Action action = () =>
                            DirectiveTypeDescriptorExtensions
                            .Ignore <CustomDirective2>(null, t => t.Argument2);

            // assert
            Assert.Throws <ArgumentNullException>(action);
        }
        public void Ignore_ExpressionIsNull_ArgumentNullException()
        {
            // arrange
            DirectiveTypeDescriptor <CustomDirective2> descriptor =
                DirectiveTypeDescriptor.New <CustomDirective2>(
                    DescriptorContext.Create());

            // act
            Action action = () =>
                            DirectiveTypeDescriptorExtensions
                            .Ignore(descriptor, null);

            // assert
            Assert.Throws <ArgumentNullException>(action);
        }