[v2] Dispatcher/ServerRunner receive-path swap — replaces BaseSession (#2710)

tests/server/conftest.py

@@ -0,0 +1,46 @@
+"""Shared fixtures for server-side tests."""
+
+from collections.abc import Iterator
+
+import pytest
+from logfire.testing import CaptureLogfire, TestExporter
+from opentelemetry.sdk.trace import ReadableSpan
+
+
+class SpanCapture:
+    """Thin adapter over logfire's `TestExporter` for asserting on MCP spans.
+
+    `finished()` returns the raw `ReadableSpan` objects emitted by the
+    `mcp-python-sdk` instrumentation scope, filtered to exclude logfire's
+    synthetic `pending_span` markers, so tests can assert directly on
+    `.name`, `.kind`, `.status`, `.attributes`, `.parent`, `.events`.
+    """
+
+    def __init__(self, exporter: TestExporter) -> None:
+        self._exporter = exporter
+
+    def clear(self) -> None:
+        self._exporter.clear()
+
+    def finished(self) -> list[ReadableSpan]:
+        return [
+            s
+            for s in self._exporter.exported_spans
+            if s.instrumentation_scope is not None
+            and s.instrumentation_scope.name == "mcp-python-sdk"
+            and not (s.attributes and s.attributes.get("logfire.span_type") == "pending_span")
+        ]
+
+
+@pytest.fixture
+def spans(capfire: CaptureLogfire) -> Iterator[SpanCapture]:
+    """In-memory MCP span capture, cleared before and after each test.
+
+    Backed by the project-level `capfire` override (see `tests/conftest.py`),
+    which scopes `mcp.shared._otel._tracer` to the test so the real tracer
+    doesn't leak into later tests in the same worker.
+    """
+    capture = SpanCapture(capfire.exporter)
+    capture.clear()
+    yield capture
+    capture.clear()