test: Convert test_workspace_isolation.py to pytest style

[BukeLy]

Summary

Convert workspace isolation test suite to pytest style and fix critical test issues.

Changes

1. Convert to pytest framework

• Replace custom TestResults class with standard pytest assertions
• Add @pytest.mark.asyncio decorators to async test functions
• Add pytest fixture for test setup
• Remove custom test runner
• Reduce code from 1262 to 869 lines (31% reduction)

2. Fix Mock LLM output format

Problem: Mock LLM returned JSON format, causing extraction failures:

• WARNING: "Complete delimiter can not be found in extraction result"
• Extracted 0 entities and 0 relations
• Empty graph files (310 bytes)

Solution: Use LightRAG's tuple-delimited format:

# Before
return """{"entities": [{"name": "Test Entity"}], "relationships": []}"""

# After
return """entity<|#|>Artificial Intelligence<|#|>concept<|#|>description
entity<|#|>Machine Learning<|#|>concept<|#|>description
relation<|#|>Machine Learning<|#|>Artificial Intelligence<|#|>keywords<|#|>description
<|COMPLETE|>"""

Result: Correctly extracts 2 entities and 1 relation

3. Enhance E2E test validation

Add content-specific assertions to verify data isolation:

• Check each workspace contains only its own data
• Check no cross-workspace data leakage
• Detect data contamination between workspaces

4. Update documentation

Update file header docstring to accurately describe all 11 test scenarios.

Testing

uv run pytest tests/test_workspace_isolation.py -v

All 11 tests pass in 2.43s:

• test_pipeline_status_isolation
• test_lock_mechanism
• test_backward_compatibility
• test_multi_workspace_concurrency
• test_namespace_lock_reentrance
• test_different_namespace_lock_isolation
• test_error_handling
• test_update_flags_workspace_isolation
• test_empty_workspace_standardization
• test_json_kv_storage_workspace_isolation
• test_lightrag_end_to_end_workspace_isolation

Impact

• Improved test maintainability and CI/CD integration
• Fixed Mock LLM to produce realistic test data
• Enhanced test detection capability for data isolation
• Better documentation
• Single file changed: +407 -803 lines

Related

Based on workspace-isolation branch for PR #2366.