public void Test_Substitute()
{
var tag = "{this}";
var replacements = new List <string>()
{
"that", "that other", "and one other"
};
var mail = BasicMailBuilder
.Substitute(tag, replacements)
.Build();
var message = new SendGridMessage();
message.AddSubstitution(tag, replacements);
Assert.IsFalse(string.IsNullOrEmpty(message.Header.JsonString()));
Assert.AreEqual(message.Header.JsonString(), mail.Header.JsonString());
}