Allow dotted test filenames (*.test.py) via dot-escape in compute_module_name

changelog/14514.bugfix.rst

@@ -0,0 +1 @@
+Dots in test module filenames are now escaped with underscores to prevent ``pytest`` from misinterpreting them as package notation when computing the module name.

src/_pytest/pathlib.py

@@ -931,6 +931,7 @@ def compute_module_name(root: Path, module_path: Path) -> str | None:
         return None
     if names[-1] == "__init__":
         names.pop()
+    names = [p.replace(".", "_") for p in names]
     return ".".join(names)
 
 

testing/test_pathlib.py

@@ -1734,6 +1734,12 @@ def test_compute_module_name(tmp_path: Path) -> None:
         == "src.app.bar"
     )
 
+    assert compute_module_name(tmp_path, tmp_path / "foo.test.py") == "foo_test"
+    assert (
+        compute_module_name(tmp_path, tmp_path / "src/app/foo.test.py")
+        == "src.app.foo_test"
+    )
+
 
 def validate_namespace_package(
     pytester: Pytester, paths: Sequence[Path], modules: Sequence[str]