test: add more messages api cases

[bzp2010]

Summary by CodeRabbit

• Tests
  • Significantly expanded test coverage for the message proxying service with comprehensive end-to-end scenarios covering event ordering, error handling, streaming behavior, and format conversion flows.
  • Added extensive validation tests for various content type conversions, format compatibility, and edge case scenarios to enhance service reliability and robustness.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR extends the proxy message test suite with 577 new lines of comprehensive end-to-end test coverage for Anthropic /v1/messages proxying. Tests validate SSE streaming semantics, error event emission, tool call and image block mapping, request transformation, control forwarding, and input validation for unsupported cache control.

Changes

Anthropic Message Proxy Tests

Layer / File(s)	Summary
Test Infrastructure tests/proxy/messages.test.ts	Added buildOpenAiToolCallStreamEvents import for stream event generation.
Streaming Response Tests tests/proxy/messages.test.ts	Added tests for exact SSE event ordering with terminal message_delta stop reason/usage semantics; error event emission on mid-stream malformed tool-call chunks; and text/tool event lifecycle ordering in mixed-content streams.
Non-Streaming Response Mapping tests/proxy/messages.test.ts	Added test mapping upstream tool-call responses into Anthropic tool_use content blocks with stop reason and structured tool input.
Request Bridging & Transformations tests/proxy/messages.test.ts	Added tests for Anthropic tool_use/tool_result to upstream tool call conversion; image blocks to upstream image_url parts; tool_choice mapping (any → required mode; named → function selection); system block metadata and generation control (top_k, stop_sequences) forwarding; and rejection of unsupported cache_control at top-level and content block layers.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• api7/aisix#39: Implements the Anthropic /v1/messages proxy handler and routing logic directly validated by these new end-to-end tests.

🚥 Pre-merge checks | ✅ 6

✅ Passed checks (6 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
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.
E2e Test Quality Review	✅ Passed	True E2E tests with real app and etcd. 20 tests covering streaming, tool-calling, bridging, auth/errors. Proper isolation, clean assertions, comprehensive scenarios.
Security Check	✅ Passed	Test file with no security vulnerabilities. All credentials are test placeholders. No logging, database operations, or sensitive data exposure. Proper authorization test coverage present.
Title check	✅ Passed	The title 'test: add more messages api cases' is directly related to the changeset, which adds 577 lines of new test coverage for the messages API proxy.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch bzp/test-messages-more-cases

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