public void PinGeneration() { RegistrationModel model = new RegistrationModel(); List<string> generatedPins = new List<string>(); for (int i = 0; i < 10000; i++) { string newPin = model.GeneratePin(); if (generatedPins.Contains(newPin)) { Assert.Fail("Duplication pin found at index " + i); return; } generatedPins.Add(newPin); } }