public void Test_IncludeUniqueArg() { var mail = BasicMailBuilder .IncludeUniqueArg("key", "value") .Build(); var message = new SendGridMessage(); message.AddUniqueArgs(new Dictionary <string, string>() { { "key", "value" } }); Assert.IsFalse(string.IsNullOrEmpty(message.Header.JsonString())); Assert.AreEqual(message.Header.JsonString(), mail.Header.JsonString()); }