diff --git a/test/test_helpers.py b/test/test_helpers.py
new file mode 100644
index 00000000..346d16b2
--- /dev/null
+++ b/test/test_helpers.py
@@ -0,0 +1,40 @@
+import os
+from unittest import mock
+import pytest
+from duct import ensure_directories
+
+
+def ensure_directoiries(path: str) -> None:
+    if path.endswith(os.sep):  # If it ends in "/" (for linux) treat as a dir
+        os.makedirs(path, exist_ok=True)
+    else:
+        # Path does not end with a separator, treat the last part as a filename
+        directory = os.path.dirname(path)
+        if directory:  # If there's a directory part, create it
+            os.makedirs(directory, exist_ok=True)
+
+
+@pytest.mark.parametrize(
+    "path",
+    [
+        "directory/",
+        "nested/directory/",
+        "/abs/path/",
+    ],
+)
+@mock.patch("duct.os.makedirs")
+def test_ensure_directories_with_dirs(mock_mkdir, path):
+    ensure_directories(path)
+    mock_mkdir.assert_called_once_with(path, exist_ok=True)
+
+
+@mock.patch("duct.os.makedirs")
+def test_ensure_directories_with_file(mock_mkdir):
+    ensure_directories("just_a_file_name")
+    mock_mkdir.assert_not_called()
+
+
+@mock.patch("duct.os.makedirs")
+def test_ensure_directories_with_filepart_and_directory_part(mock_mkdir):
+    ensure_directories("nested/dir/file_name")
+    mock_mkdir.assert_called_once_with("nested/dir", exist_ok=True)