public string BuildCssClass()
        {
            Ensures.IsValid(IsValidColor(Color), "The color is supported.");

            return(new CssClassBuilder(CSS_CLASS_PREFIX)
                   .Append("gradient", () => IsGradient)
                   .Append(() => Color.GetCssClassPart(), () => Color != Color.None && Color != Color.Muted)
                   .Build());
        }
    public void ValidSucceedsWhenConditionIsTrue()
    {
        var action = () => Ensures.IsValid(true, string.Empty);

        action.Should().NotThrow <InvalidOperationException>();
    }
    public void ValidSucceedsWhenConditionIsFalse()
    {
        var action = () => Ensures.IsValid(false, "It is an error");

        action.Should().ThrowExactly <InvalidOperationException>().WithMessage("It is an error");
    }
    public void ValidGenericSucceedsWhenConditionIsTrue()
    {
        var action = () => Ensures.IsValid <Exception>(true);

        action.Should().NotThrow <Exception>();
    }
    public void ValidGenericSucceedsWhenConditionIsFalse()
    {
        var action = () => Ensures.IsValid <Exception>(false);

        action.Should().ThrowExactly <Exception>();
    }