1 files changed, 23 insertions, 0 deletions
diff --git a/setuptools/tests/namespaces.py b/setuptools/tests/namespaces.py
index 245cf8ea..34e916f5 100644
--- a/setuptools/tests/namespaces.py
+++ b/setuptools/tests/namespaces.py
@@ -28,6 +28,29 @@ def build_namespace_package(tmpdir, name):
     return src_dir
 
 
+def build_pep420_namespace_package(tmpdir, name):
+    src_dir = tmpdir / name
+    src_dir.mkdir()
+    pyproject = src_dir / "pyproject.toml"
+    namespace, sep, rest = name.rpartition(".")
+    script = f"""\
+        [build-system]
+        requires = ["setuptools"]
+        build-backend = "setuptools.build_meta"
+
+        [project]
+        name = "{name}"
+        version = "3.14159"
+        """
+    pyproject.write_text(textwrap.dedent(script), encoding='utf-8')
+    ns_pkg_dir = src_dir / namespace.replace(".", "/")
+    ns_pkg_dir.mkdir(parents=True)
+    pkg_mod = ns_pkg_dir / (rest + ".py")
+    some_functionality = f"name = {rest!r}"
+    pkg_mod.write_text(some_functionality, encoding='utf-8')
+    return src_dir
+
+
 def make_site_dir(target):
     """
     Add a sitecustomize.py module in target to cause