test(google): assert what Vertex sends, not that two settings agree

[lidge-jun]

Summary

The post-merge audit of #1739 caught a test that could not fail. It built the same
Vertex request twice — once with directGeminiWireRenames unset, once false — and
asserted the two matched. That stays true even if Vertex stopped preserving the
requested model id, because both sides would be wrong together.

These assert the content instead: Vertex puts the requested id on the wire under all
three setting values and never the -tiered spelling, and its system identity names
the requested model rather than a renamed one. The second covers a real defect #1739
fixed in passing, where Vertex sent the bare id while the identity line claimed
-tiered.

An ablation settles what the googleMode === "vertex" arm is actually worth:
deleting it leaves all 24 tests green, because Vertex builds its own aiplatform
URL from parsed.modelId and identityModelId only special-cases Cloud Code
Assist, so routedModelId never reaches Vertex either way. The arm is defensive
rather than load-bearing. It stays as a guard against a future refactor that routes
Vertex through the shared builder, and the test comment says plainly that no test
proves it fires today — claiming otherwise would be exactly the unfalsifiable
coverage this change removes.

Verification

• bun test tests/google-adapter.test.ts — 24 pass, 0 fail.
• bun test tests/google-adapter.test.ts tests/config.test.ts tests/gemini-37-flash-migration.test.ts — 210 pass, 0 fail, 879 expect() calls.
• Ablation run recorded above: branch deleted → still 24 pass, which is the finding, not a failure to fix.

Checklist

• Tests added or updated
• Docs updated — n/a, test-only change
• No credentials, request bodies, or account identifiers logged
• Targets dev

Summary by CodeRabbit

• Bug Fixes
  • Ensured Vertex model URLs retain the requested model ID without an unintended -tiered suffix.
  • Ensured Vertex identity text consistently displays the requested model ID.

[github-actions]

✅ Deterministic PR hygiene checks passed.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 4d63364f-4812-4869-94e8-77ebef5f73c1

📥 Commits

Reviewing files that changed from the base of the PR and between 9dbc5fc and 2c34396.

📒 Files selected for processing (1)

• tests/google-adapter.test.ts

Included review availability: Your plan includes up to 10 reviews per rolling hour; 8 remain after this review.

---

📝 Walkthrough

Walkthrough

The change adds Vertex-specific tests for URL generation and system identity text. The tests verify that requested model IDs remain unchanged and do not gain the -tiered suffix across rename settings.

Changes

Vertex model coverage

Layer / File(s)	Summary
Vertex wire-model regression tests tests/google-adapter.test.ts:386-424	Added coverage for Vertex URLs and system identity text. Tests cover both supported model IDs and unset, enabled, and disabled rename settings.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 2c343

This change strengthens localized Vertex request assertions without changing production behavior, and no actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: chilung-cgu

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: Google Vertex tests now assert request contents instead of comparing outputs from two settings.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/wave5-vertex-assertions

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}