public void DefaultValueProvider_GetAsNullableString(string value)
        {
            DefaultValueProvider <G> sut = new DefaultValueProvider <G>();
            IValue <G> result            = sut.GetAsNullableString(value);

            Assert.Equal(value, result.GetData());
            switch (value)
            {
            case null:
                Assert.IsAssignableFrom <INullValue <G> >(result);
                break;

            default:
                Assert.IsAssignableFrom <IValue <G, string> >(result);
                break;
            }
        }