Writing more complex tests

So far, we have only tested the very basic example of our sign-in interface rendering. However, we also want to make sure that our sign-in interface actually works and allows users to sign in. For this, we will write a new test that ensures that when a username and password are being provided, the sign-in button is clickable:

1. Create a new function, VerifyButtonIsEnabledWithUsernameAndPassword, inside the SignInTests.cs file and add the Test attribute to it.
2. Since we will use those queries more often, add the following Query objects to the SignInTests class:

   Query usernameInput = q => q.Marked("UsernameInput");
   Query passwordInput = q => q.Marked("PasswordInput");
   Query signInButton = q => q.Marked("SignInButton");

3. Now, let's simulate entering text in the username and password fields by inserting the following code into the VerifyButtonIsEnabledWithUsernameAndPassword test:

   App.ClearText(usernameInput...