refactor: assertType calls

[calebdw]

Hello!

This PR goes through and refactors all the assertType tests for consistency in the codebase:

• all assertType calls are now inside a function instead of in the top level
• the name for all these functions is test, I felt this was a better representation of what it actually is for than foo/dummy
  • where it makes sense, some calls are inside a test<Description> method
• any types needed inside the function are passed as parameters

Thanks!

[canvural]

Thank you!