tests: protect conda command

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Author: henryiii

tests/conftest.py

@@ -15,9 +15,10 @@
 
 import re
 import shutil
+import subprocess
 from pathlib import Path
 from string import Template
-from typing import Callable
+from typing import Any, Callable
 
 import pytest
 
@@ -63,6 +64,22 @@ def generate_noxfile(**option_mapping: str | bool) -> str:
     return generate_noxfile
 
 
+# This fixture will be automatically used unless the test has the 'conda' marker
+@pytest.fixture
+def prevent_conda(monkeypatch: pytest.MonkeyPatch) -> None:
+    def blocked_popen(*args: Any, **kwargs: Any) -> Any:
+        cmd = args[0]
+        msg = "Use of 'conda' command is blocked in tests without @pytest.mark.conda"
+        if (isinstance(cmd, list) and "conda" in cmd[0]) or (
+            isinstance(cmd, str) and "conda" in cmd
+        ):
+            raise RuntimeError(msg)
+        return original_popen(*args, **kwargs)
+
+    original_popen = subprocess.Popen
+    monkeypatch.setattr(subprocess, "Popen", blocked_popen)
+
+
 @pytest.hookimpl(tryfirst=True)
 def pytest_collection_modifyitems(items: list[pytest.Item]) -> None:
     for item in items:
@@ -73,3 +90,9 @@ def pytest_collection_modifyitems(items: list[pytest.Item]) -> None:
                 pytest.mark.skipif(not HAS_CONDA, reason="Missing conda command.")
             )
             item.add_marker(pytest.mark.xdist_group(name="conda"))
+
+
+# Protection to make sure every conda-using test requests it
+def pytest_runtest_setup(item: pytest.Item) -> None:
+    if not any(mark.name == "conda" for mark in item.iter_markers()):
+        item.fixturenames = [*item.fixturenames, "prevent_conda"]  # type: ignore[attr-defined]