public void NonnumericStringReturnsNull()
            {
                const string NonnumericString = "XYZ";

                var result = NonnumericString.ConvertToNullable().Int32.ParseInvariant();

                result.HasValue.Should().BeFalse();
            }
            public void NonnumericStringReturnsDefault()
            {
                const string NonnumericString = "XYZ";
                const int    DefaultValue     = 5;

                var result = NonnumericString.ConvertWithDefaultTo().Int32.ParseInvariant(DefaultValue);

                result.Should().Be(DefaultValue);
            }
            public void NonnumericStringThrows()
            {
                const string NonnumericString = "XYZ";

                Assert.Throws <FormatException>(() => NonnumericString.ConvertTo().Int32.ParseInvariant());
            }