public void EnvelopeCustomFieldsTest()
 {
     var envelope = new Envelope { Login = _account };
     byte[] doc1 = { 36, 45, 34, 67, 121, 87, 99, 32, 32, 32, 54, 54, 55, 56, 32 };
     var signers = new List<Signer>();
     signers.Add(new Signer { email = "*****@*****.**", name = "test2", recipientId = "1", routingOrder = "1" });
     envelope.Recipients = new Recipients { signers = signers.ToArray() };
     Assert.IsTrue(envelope.Create(doc1, "test-self-signed.doc"));
     Assert.IsNull(envelope.RestError);
     var fields = new Dictionary<string, object>();
     fields.Add("time", DateTime.Now);
     fields.Add("isUnitTest", true);
     fields.Add("unitTestName", "EnvelopeCustomFieldsTest");
     Assert.IsTrue(envelope.AddCustomFields(fields));
     Assert.IsNull(envelope.RestError);
     Assert.IsTrue(envelope.GetCustomFields()); 
     Assert.IsNull(envelope.RestError);
     Assert.AreEqual(3, envelope.CustomFields.textCustomFields.Length);
     Assert.AreEqual("True", envelope.CustomFields.textCustomFields[1].value);
 }