public void Invalid_Input_Empty_String_Not_Allowed()
{
const string emailAddressString = "";
var exception = Assert.Throws <DomainArgumentException>(() => EmailAddress.From(emailAddressString));
Assert.Equal("EmailAddress () : can be null but not empty.", exception.Message);
}
public void Valid_Null_Assignment_Allowed()
{
const string emailAddressString = null;
Assert.NotNull(EmailAddress.From(emailAddressString));
}