Minimize use of setup/teardown hooks (e.g. `before`, `beforeEach`, `after`, `afterEach`)

* Keeping the setup for each unit test in the individual test makes it easier to understand what behaviour it is testing. A test should be readable in isolation, without cross-referencing elaborate setup steps.
* It should be easy for the reader to understand which setup steps the test relies upon.

No files, tests, or entry points are named. Start by surveying the TypeScript test suites for before, beforeEach, after, and afterEach hooks, then determine the intended scope and replacement pattern. Done would require a project-wide, agreed reduction in hook-based setup while keeping tests readable and passing.

Written by the indexing model from the issue text.