Improved tests and testing with tox 4

tests/conftest.py

@@ -0,0 +1,36 @@
+import shutil
+
+import pytest
+from utils import FIXTURES_DIR, TOX4
+
+
+@pytest.fixture(autouse=True)
+def projdir(tmp_path, monkeypatch):
+    pwd = tmp_path / "projdir"
+    pwd.mkdir()
+    for fname in "tox.ini", "setup.py":
+        shutil.copy(FIXTURES_DIR / fname, pwd)
+    monkeypatch.chdir(pwd)
+    return pwd
+
+
+if TOX4:
+    available_options = ("--print-deps-to-file=-", "--print-deps-to=-")
+else:
+    available_options = (
+        "--print-deps-only",
+        "--print-deps-to-file=-",
+        "--print-deps-to=-",
+    )
+
+
+@pytest.fixture(params=available_options)
+def print_deps_stdout_arg(request):
+    """Argument for printing deps to stdout"""
+    return request.param
+
+
+@pytest.fixture(params=("--print-extras-to-file=-", "--print-extras-to=-"))
+def print_extras_stdout_arg(request):
+    """Argument for printing extras to stdout"""
+    return request.param