Writing tests is really simple, it's almost like telling a friend over the phone how you'd sign in to Github and what happens if the username or password is wrong.

Login to Github Test
I.fill("Email", "")
I.fill("Password", "supersecretpassword")"Sign in")
I.see("Incorrect username or password.")

Hit on the Try it button above to run the test.

When you are ready, click Next below and find out how are each of the commands used.