When does create raise error?

I am testing with rspecs on model

 u = User.create(email: 'asd@we.com', password: 'asdasdasd', admin: true, firstname: 'qwe', lastname: 'wer', grade: 5, section: 'w', role: 'teacher')
       expect(u).to be_valid

but it raises an exception if role is set to a random value for example "principal" this happens because role is an enum with two possible values "student" and "teacher"

So in this case i cannot use expect(u).to be_valid. I have to catch the exception. The error it throws is

ArgumentError:
       'principal' is not a valid role

So i am wondering what other cases does .create throw an error instead of just populating the errors in model.errors. When should i catch errors? I appreciate any help! Thanks!