[mcp-2026] Replace sidecar tests with a TestClient matrix; drop ping exports #27

Context

PR #21 added a large mcp20 test suite that mostly locks in the sidecar, not the 2026 wire:

• tests/test_mcp20_stateless_http.py ~3300 lines: StatelessIngressPipeline, header-only ping, era alias soup
• tests/test_mcp20_acceptance.py: protocol_coverage_complete() / “every enum has a row” / ping listed as a deliverable
• tests/test_mcp20_blueprint.py: import layout as conformance
• nitrostack/runtime/acceptance.py and conformance.py: ticket registries, not spec checks
• Public API exports build_ping_response, wrap_stateless_transport, StatelessIngressPipeline (nitrostack/__init__.py, nitrostack/protocol/__init__.py)
• RuntimeLayer / DispatchStage exist for the sidecar lifecycle

WP0–WP2 will break the 3k-line file on purpose. This issue replaces that suite with a small HTTP matrix and drops ping/sidecar exports.

Handoff: #21 (comment)

Do this after WP0 (unwrap) and in the same PR as or immediately after WP2 (wire assertions). Do not “fix” header-only ping tests to keep them green.

Goal

Few TestClient tests against McpApplication.get_combined_app(). Production no longer exports ping/sidecar helpers. Layout registries are not the definition of done.

Probe

wc -l tests/test_mcp20_*.py
rg -n "build_ping_response|wrap_stateless_transport|StatelessIngressPipeline|is_header_only_ping" nitrostack tests
rg -n "ACCEPTANCE_CRITERIA|PROTOCOL_DELIVERABLES|assert_blueprint_layout" nitrostack tests

Read tests/test_transport_http.py and tests/test_lifecycle_http.py for fixture style to copy. Read nitrostack/__init__.py export lists.

Implementation

1. Delete or gut tests/test_mcp20_stateless_http.py (do not keep ping fast-path cases).
2. Delete or gut layout/count tests in tests/test_mcp20_acceptance.py and tests/test_mcp20_blueprint.py.
3. Delete nitrostack/runtime/acceptance.py and conformance.py if nothing production imports them (only tests). Same for unused RuntimeLayer (protocol/layers.py) and DispatchStage if the pipeline is gone (WP0).
4. Replace with one (or two) focused modules, e.g. tests/test_mcp20_http_wire.py, using Starlette TestClient + a tiny @mcp_app like existing HTTP tests.

Matrix (era via env/config; reset DI in setup like other tests):

5. Exports. Remove build_ping_response, wrap_stateless_transport, StatelessIngressPipeline from public __init__ if WP0 deleted them. rg ping nitrostack/ empty of live RPC.

6. Concurrency tests (tests/test_mcp20_concurrency.py): if InFlightRegistry was deleted (WP3), delete tests that poke app._in_flight. Do not keep tests that require an unwired cancel map.

7. Do not bump pyproject.toml version. Do not rewrite README feature marketing unless a sentence is factually wrong (ping advertised).

Keep: tests/test_mcp20_oauth_cimd.py, schema/contracts tests that still match protocol/schema.py, MRTR helper tests if those helpers remain.

Test / verify

pytest tests/test_mcp20_http_wire.py tests/test_transport_http.py tests/test_lifecycle_http.py tests/test_oauth.py tests/test_tasks.py -q
pytest tests/test_mcp20_*.py -q

Second command should not include a 3k-line ping suite. Full pytest -q on the repo should pass or only fail on unrelated pre-existing tests — do not ignore failures in mcp20 files you kept.

Review

• New tests hit get_combined_app() (or the same Starlette app start() uses), not StatelessIngressPipeline as a unit, unless a non-RPC header-only helper remains.
• No test requires Mcp-Method: ping + garbage body → 200.
• acceptance_criteria_registered() / len(PROTOCOL_DELIVERABLES) >= 14 gone.

Success

• Header-only ping and pipeline unit file gone
• Small TestClient matrix covers discover, ping-not-found, modern headers, health
• Ping/sidecar not in public exports
• Runtime acceptance/conformance registries gone if unused
• pytest tests/test_mcp20_*.py is maintainable (order of hundreds of lines, not thousands of sidecar cases)

Related

Depends on WP0 and WP2. Coordinate WP3 Hide so task rows in the matrix match. WP4 keeps its own CIMD tests.