public void Convert_NoRegisteredConverter_ShouldThrow() { // arrange var source = new Celcius(23); var targetType = typeof(Farenheit); // act & assert _target.Invoking(t => t.Convert(source, targetType)) .ShouldThrow<ConversionNotRegisteredException>() .And.Message.Should() .Contain(source.GetType().Name) .And.Contain(targetType.Name); }