For the upcoming midterm, a good source of practice material is UPenn’s software foundations course:
In general, ignore any reference to "informal proofs", that will not be asked as we have not really focused on that in class. Some of the material regarding Imp will be covered in the next couple of weeks, so keep that in mind. You can safely ignore any multiple choice questions not covered in class.
The following are a few selected exercises from past midterms that resemble what I could ask:
18fa-mid1: Exercises 1,2,3,5,7
18fa-mid2: Exercises: None
17fa-mid1: Exercises 1,2,3,5,6
17fa-mid2: Exercises: 4, 5ab
Equivalent IMP programs