Fix flaky SDK E2E tests

[stephentoub]

Live runtime CI was timing out in SDK E2E tests for reasons unrelated to SDK behavior: tool-filtering cases waited for full assistant responses when only the outbound CAPI request shape mattered, and MCP config tests used echo/true stand-ins that are not portable stdio MCP servers on Windows.

This updates the tests to assert deterministic state instead of depending on fragile assistant completions or platform-specific commands:

• Poll captured CAPI exchanges for tool-filter assertions across SDKs.
• Use the shared Node MCP test server for real MCP subprocess tests and wait for connected status before prompting.
• Trim MCP resume tests and snapshots so they validate resumed session identity plus MCP connectivity without an unmatched second model call.
• Leave serialization-only echo fixtures alone.

Validation:

• .NET targeted MCP tests passed.
• Node targeted MCP tests passed.
• Python targeted MCP tests passed.
• Go targeted MCP tests passed.
• Rust targeted MCP tests passed.
• Java mvn verify was not run locally because this Windows session does not have a JDK installed; Java CI installs JDK 17.

[Copilot]

Pull request overview

Updates multi-language SDK E2E tests to remove flakiness caused by waiting on full assistant completions when only request/connection state matters, and replaces non-portable stdio MCP stand-ins (echo/true) with the shared Node-based MCP test server plus explicit “connected” polling.

Changes:

• Switch tool-filtering assertions (available/excluded/default-agent excluded tools) to poll captured CAPI exchanges instead of awaiting assistant completion.
• Update MCP server E2E coverage to run a real stdio MCP subprocess (test/harness/test-mcp-server.mjs) and wait for CONNECTED status before asserting/continuing.
• Trim resume snapshots/tests to validate resumed session identity and MCP connectivity without requiring an additional model turn.

Show a summary per file

File	Description
test/snapshots/mcp_and_agents/should_accept_mcp_server_configuration_on_session_resume.yaml	Removes second prompt/response turn so resume test no longer depends on an extra model call.
test/snapshots/mcp_and_agents/accept_mcp_server_config_on_resume.yaml	Same as above for Go subtest snapshot naming.
rust/tests/e2e/session.rs	Tool-filter tests now send without waiting and assert against captured CAPI exchanges.
rust/tests/e2e/rpc_mcp_and_skills.rs	Uses shared Node MCP test server script with explicit harness working directory.
python/e2e/testharness/context.py	Adds wait_for_exchanges() helper to poll for captured exchanges deterministically.
python/e2e/test_session_e2e.py	Tool-filter tests now wait for captured exchanges and always disconnect sessions.
python/e2e/test_session_config_e2e.py	Resume/tool assertions now wait for captured exchanges instead of assistant completion.
python/e2e/test_rpc_mcp_and_skills_e2e.py	Runs real MCP stdio server + waits for CONNECTED before MCP assertions.
python/e2e/test_mcp_and_agents_e2e.py	Runs real MCP stdio server + waits for CONNECTED; trims resume assertion to connectivity.
nodejs/test/e2e/session.e2e.test.ts	Tool-filter tests now poll proxy exchanges (retry) and ensure session disconnect in finally.
nodejs/test/e2e/session_config.e2e.test.ts	Resume/tool assertions now poll proxy exchanges instead of waiting on assistant completion.
nodejs/test/e2e/rpc_mcp_and_skills.e2e.test.ts	Uses shared MCP test server + waits for MCP CONNECTED before listing/asserting.
nodejs/test/e2e/mcp_and_agents.e2e.test.ts	Uses shared MCP test server + waits for MCP CONNECTED; trims resume flow to connectivity.
java/src/test/java/com/github/copilot/sdk/McpAndAgentsTest.java	Uses shared MCP test server and polls MCP status to CONNECTED; trims resume to connectivity.
java/src/test/java/com/github/copilot/sdk/E2ETestContext.java	Exposes getRepoRoot() so tests can locate shared harness assets.
go/internal/e2e/testharness/context.go	Adds WaitForExchanges polling helper for deterministic exchange capture.
go/internal/e2e/session_e2e_test.go	Tool-filter tests now assert via captured exchanges and use t.Cleanup for disconnect.
go/internal/e2e/session_config_e2e_test.go	Resume/tool assertion now sends without waiting and polls captured exchanges.
go/internal/e2e/rpc_mcp_and_skills_e2e_test.go	Uses shared MCP test server + waits for MCP CONNECTED before assertions.
go/internal/e2e/mcp_server_helpers_test.go	Adds shared helpers for MCP stdio server config + CONNECTED polling.
go/internal/e2e/mcp_and_agents_e2e_test.go	Uses shared MCP helpers; trims resume to connectivity and waits for CONNECTED where relevant.
dotnet/test/Harness/E2ETestBase.cs	Centralizes exchange polling + shared MCP server config discovery + MCP CONNECTED polling.
dotnet/test/E2E/SessionMcpAndAgentConfigE2ETests.cs	Uses shared MCP helpers; trims resume to connectivity and removes assistant-dependent assertions.
dotnet/test/E2E/SessionE2ETests.cs	Tool-filter assertions now rely on captured exchanges via helper instead of assistant completion.
dotnet/test/E2E/SessionConfigE2ETests.cs	Resume/tool assertion now uses captured exchange helper and ensures dispose in finally.
dotnet/test/E2E/RpcMcpAndSkillsE2ETests.cs	Uses shared MCP server config + waits for CONNECTED before MCP RPC assertions.
dotnet/test/E2E/PreMcpToolCallHookE2ETests.cs	Renames local harness-dir finder to avoid confusion with shared MCP harness locator.

Copilot's findings

• Files reviewed: 27/27 changed files
• Comments generated: 0

[github-actions]

Cross-SDK Consistency Review ✅

This PR modifies only test infrastructure across all language SDKs (dotnet, go, java, nodejs, python, rust) — no public SDK API surface changes were made.

The test fixes (polling CAPI exchanges for tool-filter assertions, using the shared Node MCP test server, trimming snapshot-sensitive resume tests) are applied consistently across all SDK implementations. No cross-language consistency issues were identified.

Generated by SDK Consistency Review Agent for issue #1379 · ● 1.5M · ◷