public void AddCustomer() { //Arrange var expectedFirstName = "John"; var expectedLastName = "Smith"; var expectedPhone = "1234567890"; int addSuccess = 1; MainScreen form = new MainScreen(); var createControl = form.GetType().GetMethod("CreateControl", BindingFlags.Instance | BindingFlags.NonPublic); createControl.Invoke(form, new object[] { true }); //Act - set up values //result = 1 if new customer is added, result = 0 if customer can not be added int actualResult = form.AddCustomer(expectedFirstName, expectedLastName, expectedPhone); //Assertion - The expected output given the known inputs Assert.Equal(addSuccess, actualResult); }