test: replace subprocess servers with in-process threaded servers for coverage tracking#2341
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- Replace multiprocessing.Process with threading.Thread for context_aware_server fixture (same pattern as PR modelcontextprotocol#2341) - Remove 5 pragma: no cover markers from context-aware server code - Remove dead run_server() function and unused imports - Remaining 5 pragmas are on genuinely unreachable defensive code
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Replace multiprocessing.Process with threading.Thread + uvicorn.Server for test server fixtures (basic_server, json_server, resumable_server) so coverage.py can track server-side code in the same process. Changes: - Add _start_server_thread() helper using uvicorn.Server in a daemon thread - Graceful shutdown via server.should_exit instead of proc.kill() - Remove 8 pragma: no cover from test fixtures (no longer needed) - Add 8 new tests covering previously-uncovered branches - Remove dead run_server() function and unused http_client fixture - Convert pragma: no cover to pragma: lax no cover in source files for non-deterministic coverage lines (thread timing dependent) - Add pragma: no branch for partial branch coverage on guard lines
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- Add warnings.filterwarnings in _run_server thread to suppress asyncio.iscoroutinefunction deprecation (Python 3.14+) - Add ResourceWarning filter for unclosed sockets during teardown (Windows) - Add pytest filterwarnings for DeprecationWarning and PytestUnhandledThreadExceptionWarning in pyproject.toml
Add pragma annotations for 3 remaining uncovered paths: - pragma: no branch on mcp_session_id checks in _create_error_response and initialization handler (always True in stateful manager) - pragma: lax no cover on ClosedResourceError handler (non-deterministic) Add 5 integration tests for transport validation: - POST with invalid Content-Type (400) - POST/GET/DELETE with mismatched session ID (404) - PUT unsupported method (405) All 74 tests pass with 100% coverage and strict-no-cover clean.
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Motivation
Part of #1678
The Streamable HTTP test fixtures launch servers via
multiprocessing.Process. Sincecoverage.pycannot track code in child processes by default, server-side code paths appear uncovered despite being exercised by tests, requiring# pragma: no coverworkarounds in both test and source files.Changes
Test refactoring
Replace
multiprocessing.Processwith in-processthreading.Thread+uvicorn.Serverfor the three main server fixtures (basic_server,json_server,resumable_server).coverage.pytracks all threads in the same process by default, so these code paths are now properly covered._start_server_thread(): launchesuvicorn.Serveron a daemon thread with graceful shutdown (server.should_exit = True)run_server()function and unusedtracebackimport# pragma: no covermarkers from test server codereplay_events_after(non-existent event ID, None-message skipping)slow://resource readlong_running_with_checkpointstoolmulti_close_tool/tool_with_standalone_stream_closewith and without event storehttp_clientfixtureSource file pragma adjustment
Since the test servers now run in-process,
coverage.pynow tracks source code that was previously unreachable. This requires adjusting coverage annotations to satisfy bothcoverage --fail-under=100andstrict-no-cover:# pragma: no coverfrom lines now deterministically covered# pragma: lax no coveron non-deterministicexcepthandlers (e.g. race-condition-dependentBrokenResourceError,ClosedResourceError) — these are sometimes covered depending on thread timing;laxis excluded bycoverage.py(viaexclude_lines) but not flagged bystrict-no-cover# pragma: no branchfor branch partials that are never taken in tests (e.g.mcp_session_idchecks that are always True in the stateful manager architecture)Files modified (annotation changes only, no logic changes):
src/mcp/server/streamable_http.pysrc/mcp/server/transport_security.pysrc/mcp/server/session.pyResults
pyright0 errors,ruff check+ruff formatcleanstrict-no-cover: ✅ no wrongly marked lines