Consolidate VAOS unit and e2e test utilities

[JunTaoLuo]

Summary

Currently there are some duplications between test utilities across unit and e2e tests as mentioned here. The goal of this issue is to reduce or remove these duplications so all tests share the same utility functions. This should help with improving the maintainability of the VAOS frontend tests.

Acceptance Criteria

• [ ] Investigate test utilities in:
  • [ ] src/applications/vaos/tests/e2e/fixtures
  • [ ] src/applications/vaos/tests/mocks
  • [ ] Try to eliminate duplicated functionalities and consolidate into one set of test utilities

Definition of Done

• [ ] All acceptance criteria are met

[JunTaoLuo]

Unassigning myself since I'm not currently actively working on this.