Revert "environment tests, improve thread safety"

This reverts commit 22beace.

Author: mr-c

tests/test_environment.py

@@ -190,21 +190,18 @@ def BIND(v: str, env: Env) -> bool:
 
 # CRT = container runtime
 CRT_PARAMS = pytest.mark.parametrize(
-    "crt_params_",
+    "crt_params",
     [
-        NoContainer,
-        pytest.param(Docker, marks=needs_docker),
-        pytest.param(Singularity, marks=needs_singularity),
+        NoContainer(),
+        pytest.param(Docker(), marks=needs_docker),
+        pytest.param(Singularity(), marks=needs_singularity),
     ],
 )
 
 
 @CRT_PARAMS
-def test_basic(
-    crt_params_: type[CheckHolder], tmp_path: Path, monkeypatch: pytest.MonkeyPatch
-) -> None:
+def test_basic(crt_params: CheckHolder, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
     """Test that basic env vars (only) show up."""
-    crt_params = crt_params_()
     tmp_prefix = str(tmp_path / "canary")
     extra_env = {
         "USEDVAR": "VARVAL",
@@ -224,10 +221,9 @@ def test_basic(
 
 @CRT_PARAMS
 def test_preserve_single(
-    crt_params_: type[CheckHolder], tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+    crt_params: CheckHolder, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
 ) -> None:
     """Test that preserving a single env var works."""
-    crt_params = crt_params_()
     tmp_prefix = str(tmp_path / "canary")
     extra_env = {
         "USEDVAR": "VARVAL",
@@ -253,13 +249,12 @@ def test_preserve_single(
 
 @CRT_PARAMS
 def test_preserve_single_missing(
-    crt_params_: type[CheckHolder],
+    crt_params: CheckHolder,
     tmp_path: Path,
     monkeypatch: pytest.MonkeyPatch,
     caplog: pytest.LogCaptureFixture,
 ) -> None:
     """Test that attempting to preserve an unset env var produces a warning."""
-    crt_params = crt_params_()
     tmp_prefix = str(tmp_path / "canary")
     args = crt_params.flags + [
         f"--tmpdir-prefix={tmp_prefix}",
@@ -283,10 +278,9 @@ def test_preserve_single_missing(
 
 @CRT_PARAMS
 def test_preserve_all(
-    crt_params_: type[CheckHolder], tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+    crt_params: CheckHolder, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
 ) -> None:
     """Test that preserving all works."""
-    crt_params = crt_params_()
     tmp_prefix = str(tmp_path / "canary")
     extra_env = {
         "USEDVAR": "VARVAL",