fix(firestore): add a note for devs and asserts for firestore_data_delete_collection

[eapl-gemugami]

Description

Fixes Internal: b/239029690

The sample works well, but requires manual steps before running local tests.

• Add a note for future developers before running tests (Set env vars, and create a firestore DB for testing)
• Add asserts to validate the state before deleting the collection

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• Tests pass: nox -s py-3.9 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• Please merge this PR for me once it is approved

[gemini-code-assist]

Hello @eapl-gemugami, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

Summary of Changes

Hello! Gemini here, providing a summary of this pull request. This PR aims to improve the developer experience when running the Firestore snippets tests locally. It addresses an internal issue by adding clear instructions for setting up the test environment and enhancing the robustness of the test_delete_full_collection function with explicit assertions.

Highlights

• Developer Setup Instructions: A comment block has been added to snippets_test.py to guide developers on the necessary manual steps before running tests locally, specifically setting the FIRESTORE_PROJECT environment variable and ensuring a default Firestore database exists.
• Test Assertion Improvements: Assertions have been added to the test_delete_full_collection function to verify the state of the collection before adding test data (it should be empty) and after adding data (it should contain 5 documents) before the deletion function is called.

Changelog

• firestore/cloud-client/snippets_test.py
  • Added a multi-line comment with setup instructions for local testing.
  • Added an assertion to check if the 'cities' collection is empty before adding test data in test_delete_full_collection.
  • Added an assertion to check if 5 documents were successfully added to the 'cities' collection before calling the delete function in test_delete_full_collection.

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Tests need setup,
Environment variables,
Database ready.

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[gemini-code-assist]

Code Review

This pull request adds a helpful note for developers regarding local test setup and improves the robustness of the test_delete_full_collection by adding assertions. These changes align well with the PR description and contribute to better maintainability and test reliability.

Summary of Findings

• Developer Note for Local Testing: A helpful TODO comment was added to guide developers on setting up their environment and Firestore database for running tests locally. (Note: This was a low severity issue and not commented on directly per review settings.)
• Test Assertions for Collection State: Assertions were added to test_delete_full_collection to verify the collection is empty before adding data and contains the expected number of documents after population. This improves test reliability.

Merge Readiness

The changes in this pull request are beneficial, adding useful developer guidance and improving test reliability. The identified medium severity issue is a suggestion for improvement rather than a blocker. The pull request appears ready to be merged. Please note that I am unable to approve the pull request directly; other reviewers should provide approval.