test(06-01): add 5 xfail stubs for structured logging (D-01/D-02)

- test_setup_logging_emits_json_when_LOG_JSON_true
- test_correlation_id_middleware_binds_contextvar
- test_correlation_id_response_header_present
- test_contextvars_cleared_between_requests (Pitfall 2 guard)
- test_uvicorn_access_log_suppressed
All strict=False xfail stubs; implementation target: plan 06-02

backend/tests/test_logging.py

@@ -0,0 +1,52 @@
+"""
+Structured logging test stubs — D-01, D-02.
+
+Wave 0 xfail scaffold for Phase 6 plan 06-02.
+
+All tests use strict=False so an unexpected pass during development
+never breaks CI. Implementation lands in plan 06-02.
+"""
+from __future__ import annotations
+
+import pytest
+
+
+# ── D-01: JSON renderer wired through ProcessorFormatter ─────────────────────
+
+@pytest.mark.xfail(strict=False, reason="implementation in 06-02")
+async def test_setup_logging_emits_json_when_LOG_JSON_true():
+    """setup_logging(json_logs=True) installs JSONRenderer through
+    ProcessorFormatter and the root logger emits JSON to stdout."""
+    pytest.xfail("not implemented yet")
+
+
+# ── D-02: CorrelationIDMiddleware binds structlog contextvars ─────────────────
+
+@pytest.mark.xfail(strict=False, reason="implementation in 06-02")
+async def test_correlation_id_middleware_binds_contextvar(async_client):
+    """CorrelationIDMiddleware binds correlation_id, path, and method into
+    structlog.contextvars for every inbound HTTP request."""
+    pytest.xfail("not implemented yet")
+
+
+@pytest.mark.xfail(strict=False, reason="implementation in 06-02")
+async def test_correlation_id_response_header_present(async_client):
+    """Every HTTP response includes an X-Correlation-ID header set to the
+    correlation_id bound by CorrelationIDMiddleware."""
+    pytest.xfail("not implemented yet")
+
+
+@pytest.mark.xfail(strict=False, reason="implementation in 06-02")
+async def test_contextvars_cleared_between_requests(async_client):
+    """Pitfall 2 guard: clear_contextvars() runs first in the middleware so
+    user_id from a prior request never bleeds into the next request's log context."""
+    pytest.xfail("not implemented yet")
+
+
+# ── D-01 / uvicorn log suppression ───────────────────────────────────────────
+
+@pytest.mark.xfail(strict=False, reason="implementation in 06-02")
+async def test_uvicorn_access_log_suppressed():
+    """uvicorn.access propagate=False after setup_logging() so the
+    CorrelationIDMiddleware owns request logging and access lines are not doubled."""
+    pytest.xfail("not implemented yet")