Ensure pytest runs without optional plugins

Author: SaridakisStamatisChristos

tests/conftest.py

@@ -0,0 +1,60 @@
+from __future__ import annotations
+
+import importlib.util
+import os
+import sys
+from pathlib import Path
+
+from _pytest.config import Config
+from _pytest.config.argparsing import Parser
+
+PROJECT_ROOT = Path(__file__).resolve().parents[1]
+SRC_PATH = PROJECT_ROOT / "src"
+if SRC_PATH.is_dir():
+    src_str = str(SRC_PATH)
+    if src_str not in sys.path:
+        sys.path.insert(0, src_str)
+
+    existing = os.environ.get("PYTHONPATH")
+    if existing:
+        if src_str not in existing.split(os.pathsep):
+            os.environ["PYTHONPATH"] = os.pathsep.join([src_str, existing])
+    else:
+        os.environ["PYTHONPATH"] = src_str
+
+_HAS_PYTEST_COV = importlib.util.find_spec("pytest_cov") is not None
+
+
+def pytest_addoption(parser: Parser) -> None:
+    """Register no-op coverage flags when pytest-cov is unavailable."""
+
+    if _HAS_PYTEST_COV:
+        return
+
+    group = parser.getgroup("cov (missing plugin)")
+    group.addoption(
+        "--cov",
+        action="append",
+        dest="cov",
+        default=[],
+        metavar="PATH",
+        help="coverage reporting requires pytest-cov; option accepted but ignored.",
+    )
+    group.addoption(
+        "--cov-report",
+        action="append",
+        dest="cov_report",
+        default=[],
+        help="coverage reporting requires pytest-cov; option accepted but ignored.",
+    )
+
+
+def pytest_configure(config: Config) -> None:
+    if _HAS_PYTEST_COV:
+        return
+
+    if getattr(config.option, "cov", None) or getattr(config.option, "cov_report", None):
+        config.issue_config_time_warning(
+            "pytest-cov is not installed; coverage options are ignored.",
+            stacklevel=2,
+        )