Drop explicit checks from is_namespace_package and add tests

src/_pytest/pathlib.py

@@ -795,16 +795,14 @@ def resolve_pkg_root_and_module_name(
 def _is_namespace_package(module_path: Path) -> bool:
     module_name = module_path.name
 
-    # Empty module names break find_spec.
+    # Empty module names (such as Path.cwd()) might break meta_path hooks (like our own assertion rewriter).
     if not module_name:
         return False
 
-    # Modules starting with "." indicate relative imports and break find_spec, and we are only attempting
-    # to find top-level namespace packages anyway.
-    if module_name.startswith("."):
+    try:
+        spec = importlib.util.find_spec(module_name)
+    except ImportError:
         return False
-
-    spec = importlib.util.find_spec(module_name)
     if spec is not None and spec.submodule_search_locations:
         # Found a spec, however make sure the module_path is in one of the search locations --
         # this ensures common module name like "src" (which might be in sys.path under different locations)

testing/test_pathlib.py

@@ -17,6 +17,7 @@ from typing import Tuple
 import unittest.mock
 
 from _pytest.monkeypatch import MonkeyPatch
+from _pytest.pathlib import _is_namespace_package
 from _pytest.pathlib import bestrelpath
 from _pytest.pathlib import commonpath
 from _pytest.pathlib import CouldNotResolvePathError
@@ -1311,3 +1312,15 @@ class TestNamespacePackages:
             tmp_path / "src/dist1",
             "com.company.app.core.models",
         )
+
+    def test_is_namespace_package_bad_arguments(self, pytester: Pytester) -> None:
+        pytester.syspathinsert()
+        path = pytester.path / "bar.x"
+        path.mkdir()
+        assert _is_namespace_package(path) is False
+
+        path = pytester.path / ".bar.x"
+        path.mkdir()
+        assert _is_namespace_package(path) is False
+
+        assert _is_namespace_package(Path()) is False