I forgot to include these in 63eb6672eac794a9c39dec87db3aa45147e06974
(This is fine because noone but me touched these files since the initial
change in db7ef3f02517f9f2a3c56829a22b9fad3c36e374).
The `is` operator performs object identity comparison. Changing to `==`
implements the expected behavior.
Use the mock library to add tests verifying the API of questions.yn.