You can't test every permutation of app usage. You actually need good architechture so you can trust your test and changes to be local with minimal side-effects.
In that situation you have two choices:
1. Tell claude to iterate until the tests for the new view and the old views are all passing.
2. git reset --hard back to the previous commit at which all tests are passing and tell claude to try again, making sure not to break any tests.
It's essential to use tests when vibecoding anything non trivial. Almost certainly in a TDD style.