fix(test): add environment cleanup for Vertex AI GPT-OSS tests

[jquinter]

Summary

Fixes test isolation issue in Vertex AI GPT-OSS tests by adding environment variable cleanup.

Problem

Test test_vertex_ai_gpt_oss_reasoning_effort was failing in CI with:

litellm.exceptions.AuthenticationError: Vertex_aiException - {
  "error": {
    "code": 401,
    "message": "Request had invalid authentication credentials..."
  }
}

Previous tests set Google/Vertex AI environment variables (GOOGLE_APPLICATION_CREDENTIALS, VERTEXAI_PROJECT, etc.) and don't clean them up, causing this test to attempt real Google authentication instead of using mocks.

Root Cause

Environment variable pollution from other Vertex AI tests that don't clean up after themselves.

Solution

Added clean_vertex_env pytest fixture with autouse=True to:

1. Save and clear all Google/Vertex AI environment variables before each test
2. Restore them after each test completes

This ensures each test starts with a clean environment.

Testing

Locally (without vertexai SDK):

• Test fails with ModuleNotFoundError: No module named 'vertexai' (expected)
• Does NOT try to authenticate ✅

In CI (with vertexai SDK):

• Should no longer attempt real API calls
• Mocks will be used correctly

Related

This test failure was reported on PR #21217, but NOT caused by PR #21217 (which only modifies Anthropic structured output tests). This is another test isolation issue affecting multiple Vertex AI tests.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
litellm	Ready	Preview, Comment	Feb 15, 2026 10:27pm

[greptile-apps]

Greptile Summary

Adds a pytest autouse fixture to the Vertex AI GPT-OSS test file that saves, clears, and restores Google/Vertex AI environment variables around each test. This prevents test isolation failures where leaked credentials from prior tests cause real authentication attempts instead of using mocks.

• The fixture correctly uses the save-clear-yield-restore pattern and applies to all tests in the module (both class-based and standalone async tests).
• The approach is consistent with the similar fix recently applied to the Vertex AI rerank tests.
• Minor suggestion: VERTEXAI_LOCATION and VERTEXAI_CREDENTIALS are also checked by the Vertex AI base code but are absent from the cleanup list.

Confidence Score: 4/5

• This PR is safe to merge — it only modifies test infrastructure to improve test isolation without changing production code.
• The change is a straightforward test fixture addition that follows an established pattern already used in the rerank test file. It correctly prevents environment variable leakage between tests. The only minor gap is that a couple of additional Vertex AI environment variables (VERTEXAI_LOCATION, VERTEXAI_CREDENTIALS) could also be cleaned up for completeness, but this doesn't affect the correctness of the current fix.
• No files require special attention — this is a test-only change with no production code impact.

Important Files Changed

Filename	Overview
tests/test_litellm/llms/vertex_ai/vertex_ai_partner_models/gpt_oss/test_vertex_ai_gpt_oss_transformation.py	Adds autouse pytest fixture to save/clear/restore Google/Vertex AI environment variables before and after each test, preventing test isolation issues from leaked credentials. The fix is correct and follows the same pattern as the rerank test cleanup.

Sequence Diagram

sequenceDiagram
    participant Pytest as Pytest Runner
    participant Fixture as clean_vertex_env fixture
    participant Env as os.environ
    participant Test as Test Function
    participant Mock as Mock (VertexLLM)

    Pytest->>Fixture: Before each test (autouse)
    Fixture->>Env: Save GOOGLE_APPLICATION_CREDENTIALS, VERTEXAI_PROJECT, etc.
    Fixture->>Env: Delete saved env vars
    Fixture->>Test: yield (run test)
    Test->>Mock: patch VertexLLM._ensure_access_token
    Mock-->>Test: Return ("fake-token", "project-id")
    Test->>Mock: litellm.acompletion(...)
    Mock-->>Test: Mock response (no real API call)
    Test->>Fixture: Test complete
    Fixture->>Env: Restore saved env vars

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