public void WhenProvingACustomNumberFormatShouldReturnValuesForThatFormat()
{
const double DoubleProperty = 13.8;
FormatableObject formatableObject = new FormatableObject
{
DoubleProperty = DoubleProperty
};
string str = formatableObject.ToString("{DoubleProperty:F}");
str.Should().Be(DoubleProperty.ToString("F"), "because we are using a format string to get the value of the 'DoubleProperty' property with a format");
}