public void OnePresentInAndNoPresentOutWillBeInvalid()
 {
     ExchangeCheckSum subject = new ExchangeCheckSum();
     subject.updatePresentsIn();
     Assert.AreEqual(false, subject.isValid());
     VerifyDiagnosticMessage(1, 0, subject.DiagnosticMessage());
 }
 public void OnePresentInAndOnePresentOutWillBeValid()
 {
     ExchangeCheckSum subject = new ExchangeCheckSum();
     subject.updatePresentsIn();
     subject.updatePresentsOut();
     Assert.AreEqual(true, subject.isValid());
     Assert.AreEqual("correct", subject.DiagnosticMessage());
 }
 public void ConstructedCheckSumIsNotValid()
 {
     ExchangeCheckSum subject = new ExchangeCheckSum();
     Assert.AreEqual(false, subject.isValid());
     Assert.AreEqual("not buying or recieving a gift", subject.DiagnosticMessage());
 }