tests: add conda marker (#969)

* tests: add conda marker
* Update tests/conftest.py


---------

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

Author: henryiii

pyproject.toml

@@ -144,6 +144,9 @@ filterwarnings = [ "error" ]
 log_cli_level = "INFO"
 testpaths = [ "tests" ]
 pythonpath = [ ".github/" ]
+markers = [
+  "conda: test requires conda",
+]
 
 [tool.coverage]
 run.branch = true

tests/conftest.py

@@ -14,12 +14,16 @@
 from __future__ import annotations
 
 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
 
+HAS_CONDA = shutil.which("conda") is not None
+
 
 @pytest.fixture(autouse=True)
 def reset_color_envvars(monkeypatch: pytest.MonkeyPatch) -> None:
@@ -58,3 +62,33 @@ def generate_noxfile(**option_mapping: str | bool) -> str:
         return str(path)
 
     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][0] if isinstance(args[0], list) else args[0]
+        msg = "Use of 'conda' command is blocked in tests without @pytest.mark.conda"
+        if "conda" in cmd or "mamba" in cmd:
+            raise RuntimeError(msg)
+        return original_popen(*args, **kwargs)
+
+    original_popen = subprocess.Popen
+    monkeypatch.setattr(subprocess, "Popen", blocked_popen)
+
+
+def pytest_collection_modifyitems(items: list[pytest.Item]) -> None:
+    for item in items:
+        if "make_conda" in getattr(item, "fixturenames", ()):
+            item.add_marker("conda")
+        if "conda" in item.keywords:
+            item.add_marker(
+                pytest.mark.skipif(not HAS_CONDA, reason="Missing conda command.")
+            )
+
+
+# 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.add_marker(pytest.mark.usefixtures("prevent_conda"))

tests/test_sessions.py

@@ -40,9 +40,6 @@
 from nox import _options
 from nox.logger import logger
 
-HAS_CONDA = shutil.which("conda") is not None
-has_conda = pytest.mark.skipif(not HAS_CONDA, reason="Missing conda command.")
-
 DIR = Path(__file__).parent.resolve()
 
 
@@ -1225,7 +1222,7 @@ def test__create_venv(self, create: mock.Mock) -> None:
                 "nox.virtualenv.CondaEnv.create",
                 "conda",
                 nox.virtualenv.CondaEnv,
-                marks=has_conda,
+                marks=pytest.mark.conda,
             ),
         ],
     )

tests/test_virtualenv.py

@@ -39,13 +39,11 @@
     from nox.virtualenv import CondaEnv, ProcessEnv, VirtualEnv
 
 IS_WINDOWS = sys.platform.startswith("win")
-HAS_CONDA = shutil.which("conda") is not None
 HAS_UV = shutil.which("uv") is not None
 RAISE_ERROR = "RAISE_ERROR"
 VIRTUALENV_VERSION = metadata.version("virtualenv")
 
 has_uv = pytest.mark.skipif(not HAS_UV, reason="Missing uv command.")
-has_conda = pytest.mark.skipif(not HAS_CONDA, reason="Missing conda command.")
 
 
 class TextProcessResult(NamedTuple):
@@ -171,7 +169,6 @@ def test_condaenv_constructor_explicit(
     assert venv.reuse_existing is True
 
 
-@has_conda
 def test_condaenv_create(make_conda: Callable[..., tuple[CondaEnv, Path]]) -> None:
     venv, dir_ = make_conda()
     venv.create()
@@ -200,7 +197,6 @@ def test_condaenv_create(make_conda: Callable[..., tuple[CondaEnv, Path]]) -> No
     assert venv._reused
 
 
-@has_conda
 def test_condaenv_create_with_params(
     make_conda: Callable[..., tuple[CondaEnv, Path]],
 ) -> None:
@@ -214,7 +210,6 @@ def test_condaenv_create_with_params(
         assert dir_.joinpath("bin", "pip").exists()
 
 
-@has_conda
 def test_condaenv_create_interpreter(
     make_conda: Callable[..., tuple[CondaEnv, Path]],
 ) -> None:
@@ -230,7 +225,6 @@ def test_condaenv_create_interpreter(
         assert dir_.joinpath("bin", "python3.12").exists()
 
 
-@has_conda
 def test_conda_env_create_verbose(
     make_conda: Callable[..., tuple[CondaEnv, Path]],
 ) -> None:
@@ -262,13 +256,11 @@ def test_condaenv_bin_windows(make_conda: Callable[..., tuple[CondaEnv, Path]])
     ] == venv.bin_paths
 
 
-@has_conda
 def test_condaenv_(make_conda: Callable[..., tuple[CondaEnv, Path]]) -> None:
     venv, _dir = make_conda()
     assert not venv.is_offline()
 
 
-@has_conda
 def test_condaenv_detection(make_conda: Callable[..., tuple[CondaEnv, Path]]) -> None:
     venv, dir_ = make_conda()
     venv.create()
@@ -556,7 +548,7 @@ def test_not_stale_virtualenv_environment(
     assert reused
 
 
-@has_conda
+@pytest.mark.conda
 def test_stale_virtualenv_to_conda_environment(
     make_one: Callable[..., tuple[VirtualEnv | ProcessEnv, Path]],
 ) -> None:
@@ -571,7 +563,7 @@ def test_stale_virtualenv_to_conda_environment(
     assert not reused
 
 
-@has_conda
+@pytest.mark.conda
 def test_reuse_conda_environment(
     make_one: Callable[..., tuple[VirtualEnv | ProcessEnv, Path]],
 ) -> None:
@@ -587,7 +579,7 @@ def test_reuse_conda_environment(
 
 
 # This mocks micromamba so that it doesn't need to be installed.
-@has_conda
+@pytest.mark.conda
 def test_micromamba_environment(
     make_one: Callable[..., tuple[VirtualEnv | ProcessEnv, Path]],
     monkeypatch: pytest.MonkeyPatch,
@@ -612,7 +604,7 @@ def test_micromamba_environment(
     "params",
     [["--channel=default"], ["-cdefault"], ["-c", "default"], ["--channel", "default"]],
 )
-@has_conda
+@pytest.mark.conda
 def test_micromamba_channel_environment(
     make_one: Callable[..., tuple[VirtualEnv, Path]],
     monkeypatch: pytest.MonkeyPatch,
@@ -643,7 +635,7 @@ def test_micromamba_channel_environment(
         ("venv", "virtualenv", True),
         ("virtualenv", "uv", True),
         pytest.param("uv", "virtualenv", False, marks=has_uv),
-        pytest.param("conda", "virtualenv", False, marks=has_conda),
+        pytest.param("conda", "virtualenv", False, marks=pytest.mark.conda),
     ],
 )
 def test_stale_environment(