Test cases are somewhat limited and chosen ad-hoc currently. Additional test cases (particularly ensuring good coverage over popular classes) would ensure changes for one type of bug don't cause worse overall performance.

Standalone numbers are usually classes with an implicit department, but in some cases they are instead AP scores. This leads to an incorrect prerequisite of CHEM 4 for CHEM 31X when parsing this description:

Prerequisites: AP chemistry score of 5 or passing score on chemistry placement test, and AP Calculus AB score of 4 or Math 20 or Math 41

In some cases, departments are in a nonstandard form, specifically not all-caps or using an abbreviation. Fixing this in the general case will likely require better awareness of what are valid departments in extract_courses to avoid too many false positives.

See examples below:

• In PHYSICS 120, PHYSICS is abbreviated as PHYS:

Prerequisites: PHYSICS 43 or PHYS 63; MATH 52 and MATH 53

• In CHEM 31X, MATH is written as Math

Prerequisites: AP chemistry score of 5 or passing score on chemistry placement test, and AP Calculus AB score of 4 or Math 20 or Math 41

There is no distinction given between requirements that are equivalent ("PHYSICS 43 or 63") and those that are both necessary ("MATH 52 and 53") for a course. For potential use cases like automated scheduling, this information would be useful.