fix(test): add environment cleanup for Vertex AI rerank tests

[jquinter]

Summary

Fixes test isolation issue in test_vertex_ai_rerank_transformation.py by adding proper environment variable cleanup.

Problem

• Test passes in isolation ✅
• Test fails in CI with DefaultCredentialsError: Your default credentials were not found ❌
• Previous tests set Google/Vertex AI environment variables (GOOGLE_APPLICATION_CREDENTIALS, VERTEXAI_PROJECT, etc.) and don't clean them up
• When this test runs, it attempts real Google authentication instead of using mocks
• This causes authentication failures in CI

Root Cause

Environment variable pollution from other tests that use Vertex AI/Google Cloud credentials:

• tests/litellm_utils_tests/test_secret_manager.py
• tests/pass_through_tests/test_vertex_ai.py
• tests/unified_google_tests/base_google_test.py
• tests/pass_through_unit_tests/test_unit_test_passthrough_router.py
• etc.

Solution

Added setup_method and teardown_method to:

1. setup_method: Save and clear all Google/Vertex AI environment variables before each test
2. teardown_method: Restore saved environment variables after each test

This ensures each test starts with a clean environment regardless of what previous tests did.

Testing

# All 17 tests pass locally
pytest tests/test_litellm/llms/vertex_ai/rerank/test_vertex_ai_rerank_transformation.py -v
======================= 17 passed in 0.17s ========================

Related

This is another test isolation issue affecting PR #21217 (Anthropic structured output test). NOT caused by PR #21217 - that PR only modifies Anthropic test expectations.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
litellm	Ready	Preview, Comment	Feb 15, 2026 9:28pm

[greptile-apps]

Greptile Summary

Adds proper environment variable cleanup to TestVertexAIRerankTransform to fix test isolation issues in CI. The setup_method now saves and clears 6 Google/Vertex AI environment variables (GOOGLE_APPLICATION_CREDENTIALS, GOOGLE_CLOUD_PROJECT, VERTEXAI_PROJECT, VERTEX_PROJECT, VERTEX_LOCATION, VERTEX_AI_PROJECT), and teardown_method restores them after each test.

• Prevents DefaultCredentialsError failures caused by env var pollution from other test files that set Google Cloud credentials without cleaning up
• Uses a standard save-and-restore pattern consistent with other test fixtures in the codebase
• All 17 existing tests continue to pass; no behavioral changes to test logic

Confidence Score: 5/5

• This PR is safe to merge — it only modifies test infrastructure with a well-understood save/restore pattern.
• The change is minimal, limited to test setup/teardown, uses a standard pattern seen elsewhere in the codebase, and does not affect production code. The env vars being cleared are comprehensive for the Vertex AI authentication path. The teardown properly restores original values.
• No files require special attention.

Important Files Changed

Filename	Overview
tests/test_litellm/llms/vertex_ai/rerank/test_vertex_ai_rerank_transformation.py	Adds environment variable save/clear in setup_method and restore in teardown_method to prevent test isolation issues from leaked Google/Vertex AI credentials. Clean implementation with proper save-and-restore pattern.

Flowchart

flowchart TD
    A["Test Runner: Begins test method"] --> B["setup_method()"]
    B --> C["Save existing Google/Vertex AI env vars\nto self._saved_env"]
    C --> D["Clear env vars:\nGOOGLE_APPLICATION_CREDENTIALS\nGOOGLE_CLOUD_PROJECT\nVERTEXAI_PROJECT\nVERTEX_PROJECT\nVERTEX_LOCATION\nVERTEX_AI_PROJECT"]
    D --> E["Initialize VertexAIRerankConfig\nand model"]
    E --> F["Run test method\n(mocked, no real auth)"]
    F --> G["teardown_method()"]
    G --> H["Restore saved env vars\nfrom self._saved_env"]
    H --> I["Test Runner: Next test method"]

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