fix(benchmarks): skip benchmark tests without pytest-codspeed

tests/benchmarks/conftest.py

@@ -1,4 +1,10 @@
-"""Shared fixtures and constants for benchmarks."""
+"""Shared fixtures and constants for benchmarks.
+
+Benchmark tests require the ``benchmark`` fixture provided by the
+``pytest-codspeed`` plugin. When the plugin is absent (e.g. downstream
+packaging like conda-forge running ``pytest tests/``), the tests must be
+skipped instead of failing on a missing fixture or an unknown mark.
+"""
 
 import numpy as np
 import pytest
@@ -11,6 +17,8 @@
 
 CONTINUOUS_METRICS = ["lc", "rc", "gv"]
 
+_BENCHMARK_FIXTURES = {"benchmark", "codspeed_benchmark"}
+
 
 def gen_continuous(n_nodes: int, rng: int = 19425) -> np.ndarray:
     _, _, ts = gen_delayed_causal_network(
@@ -24,14 +32,38 @@ def continuous_data(request) -> np.ndarray:
     return gen_continuous(request.param)
 
 
+def pytest_configure(config):
+    """Register the benchmark markers so they are not "unknown" without pytest-codspeed.
+
+    Without this, pytest raises a ``PytestUnknownMarkWarning`` for
+    ``@pytest.mark.benchmark`` which is escalated to an error by the
+    ``filterwarnings = ["error"]`` setting in ``pyproject.toml``.
+    """
+    existing = set()
+    for entry in config.getini("markers"):
+        name = entry.split(":", 1)[0].strip() if isinstance(entry, str) else entry[0]
+        existing.add(name)
+    for marker in sorted(_BENCHMARK_FIXTURES):
+        if marker not in existing:
+            config.addinivalue_line(
+                "markers",
+                f"{marker}: micro-benchmark; run with --codspeed",
+            )
+
+
+def _is_benchmark_item(item: pytest.Item) -> bool:
+    return bool(_BENCHMARK_FIXTURES.intersection(getattr(item, "fixturenames", [])))
+
+
 def pytest_collection_modifyitems(config, items):
+    """Skip benchmark tests unless explicitly run with ``--codspeed``.
+
+    Works with or without the ``pytest-codspeed`` plugin installed: benchmark
+    tests are identified by the ``benchmark`` fixture they request, so they are
+    skipped even when the plugin (and thus the fixture) is unavailable.
+    """
     if not config.getoption("codspeed", False):
-        try:
-            from pytest_codspeed.plugin import has_benchmark_fixture
-
-            msg = pytest.mark.skip(reason="use --codspeed to run benchmarks")
-            for item in items:
-                if has_benchmark_fixture(item):
-                    item.add_marker(msg)
-        except ImportError:
-            pass
+        msg = pytest.mark.skip(reason="use --codspeed to run benchmarks")
+        for item in items:
+            if _is_benchmark_item(item):
+                item.add_marker(msg)

tests/benchmarks/test_conftest_skip.py

@@ -0,0 +1,66 @@
+"""Regression tests for the benchmark skip logic in ``tests/benchmarks/conftest.py``.
+
+Benchmark tests must be skipped when ``--codspeed`` is not passed, and this must
+work even when the ``pytest-codspeed`` plugin (which provides the ``benchmark``
+fixture and registers the ``benchmark`` mark) is not installed -- e.g. when a
+downstream consumer such as conda-forge runs ``pytest tests/``.
+"""
+
+import pytest
+
+from .conftest import _is_benchmark_item, pytest_collection_modifyitems
+
+
+class _StubItem:
+    """Minimal stand-in for a pytest item to exercise the collection hook."""
+
+    def __init__(self, fixturenames):
+        self.fixturenames = fixturenames
+        self.own_markers = []
+
+    def add_marker(self, marker):
+        self.own_markers.append(marker)
+
+
+def test_is_benchmark_item_detects_benchmark_fixture():
+    """A test requesting the ``benchmark`` fixture is identified as a benchmark."""
+    # Arrange
+    item = _StubItem(["benchmark", "continuous_data"])
+    # Act
+    is_benchmark = _is_benchmark_item(item)
+    # Assert
+    assert is_benchmark
+
+
+def test_is_benchmark_item_false_without_benchmark_fixture():
+    """A test without a benchmark fixture is not identified as a benchmark."""
+    # Arrange
+    item = _StubItem(["continuous_data"])
+    # Act
+    is_benchmark = _is_benchmark_item(item)
+    # Assert
+    assert not is_benchmark
+
+
+def test_benchmark_item_skipped_without_codspeed(pytestconfig, monkeypatch):
+    """Without ``--codspeed``, benchmark tests are marked to be skipped."""
+    # Arrange
+    monkeypatch.setattr(pytestconfig, "getoption", lambda name, default=None: default)
+    item = _StubItem(["benchmark", "continuous_data"])
+    # Act
+    pytest_collection_modifyitems(pytestconfig, [item])
+    # Assert
+    assert any(m.mark.name == "skip" for m in item.own_markers)
+
+
+def test_benchmark_item_not_skipped_with_codspeed(pytestconfig, monkeypatch):
+    """With ``--codspeed``, benchmark tests are not skipped."""
+    # Arrange
+    monkeypatch.setattr(
+        pytestconfig, "getoption", lambda name, default=None: name == "codspeed"
+    )
+    item = _StubItem(["benchmark", "continuous_data"])
+    # Act
+    pytest_collection_modifyitems(pytestconfig, [item])
+    # Assert
+    assert not any(m.mark.name == "skip" for m in item.own_markers)