Add function to ensure a non-empty string.

tests/unit/utils/test_non_empty_str.py

@@ -0,0 +1,30 @@
+# Copyright 2026 jCloud Services GbR
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from src.jcloud_docsgen.utils import non_empty_str
+import pytest
+
+@pytest.mark.parametrize('value,expected', [
+    (None, None),
+    ('', None),
+    (' ', None),
+    ('  ', None),
+    ('   ', None),
+    (' a ', ' a '),
+    (' a', ' a'),
+    ('a ', 'a '),
+    ('a', 'a'),
+])
+def test_non_empty_str(value, expected):
+    assert non_empty_str(value) == expected