[SPIKE] Detail approach for first integration test case

Detail #19611

**Acceptance criteria**
- Add details to the aforementioned ticket so that any engineer working on the extension codebase can pick it up and do it.
- What are the key parts of the solution:
- code needed
- imported libraries or components
- test infrastructure changes
- assertions needed
- mocking/stubbing approach

Start by opening linked issue #19611 and reading the extension codebase's existing integration-test setup; this issue names no files, entry points, or test commands. Done means documenting the code, imports, test-infrastructure changes, assertions, and mocking or stubbing approach well enough for another engineer to implement the first integration test.

Written by the indexing model from the issue text.