test: add test for _flatten_message

Author: vchudnov-g

google/api_core/_python_version_support.py

@@ -144,7 +144,7 @@ class VersionInfo(NamedTuple):
 
 def _flatten_message(text: str) -> str:
     """Dedent a multi-line string and flatten it into a single line."""
-    return textwrap.dedent(text).strip().replace("\n", " ")
+    return " ".join(textwrap.dedent(text).strip().split())
 
 
 # TODO(https://github.com/googleapis/python-api-core/issues/835): Remove once we

tests/unit/test_python_version_support.py

@@ -22,6 +22,7 @@
 
 # Code to be tested
 from google.api_core._python_version_support import (
+    _flatten_message,
     check_python_version,
     PythonVersionStatus,
     PYTHON_VERSION_INFO,
@@ -31,6 +32,17 @@
 VersionInfoMock = namedtuple("VersionInfoMock", ["major", "minor"])
 
 
+def test_flatten_message():
+    """Test that _flatten_message correctly dedents and flattens a string."""
+    input_text = """
+        This is a multi-line
+        string with some
+            indentation.
+    """
+    expected_output = "This is a multi-line string with some indentation."
+    assert _flatten_message(input_text) == expected_output
+
+
 def _create_failure_message(
     expected, result, py_version, date, gapic_dep, py_eol, eol_warn, gapic_end
 ):