Anim: Add Python unit tests for vertex group Normalize All operator

Follow-up to #147272. These tests are not exhaustive, but protect
against regression of bug #147009.

Pull Request: https://projects.blender.org/blender/blender/pulls/147422

tests/python/CMakeLists.txt

@@ -604,6 +604,13 @@ if(TEST_SRC_DIR_EXISTS)
     --
     --testdir "${TEST_SRC_DIR}/animation"
   )
+
+  add_blender_test(
+    vertex_group_painting
+    --python ${CMAKE_CURRENT_LIST_DIR}/vertex_group_painting.py
+    --
+    --testdir "${TEST_SRC_DIR}/animation"
+  )
 endif()
 
 # ------------------------------------------------------------------------------

tests/python/vertex_group_painting.py

@@ -0,0 +1,76 @@
+# SPDX-FileCopyrightText: 2025 Blender Authors
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+import unittest
+import sys
+import pathlib
+
+import bpy
+
+"""
+blender -b --factory-startup --python tests/python/vertex_group_paint.py -- --testdir tests/files/animation/
+"""
+
+
+class NormalizeAllTest(unittest.TestCase):
+    """Test for normalizing all vertex groups on a mesh."""
+
+    def setUp(self) -> None:
+        bpy.ops.wm.read_homefile(use_factory_startup=True)
+        self._load_test_file()
+
+        # Make sure the initial state is what we expect/need for the tests.
+        self.cube = bpy.data.objects['Cube']
+        self.assertEqual(bpy.context.active_object, self.cube)
+        self.assertEqual(len(self.cube.vertex_groups), 2)
+
+    def _load_test_file(self):
+        blendpath = str(args.testdir / "vertex_groups.blend")
+        bpy.ops.wm.read_homefile(use_factory_startup=True)  # Just to be sure.
+        bpy.ops.wm.open_mainfile(filepath=blendpath, load_ui=False)
+
+    def test_normalize_all(self):
+        # Initial state.
+        self.cube.data.vertices[0].groups[0].weight = 0.375
+        self.cube.data.vertices[0].groups[1].weight = 0.125
+        self.cube.vertex_groups[0].lock_weight = False
+        self.cube.vertex_groups[1].lock_weight = False
+
+        # Attempt to normalize all vertex groups.  Should succeed.
+        bpy.ops.object.vertex_group_normalize_all(group_select_mode='ALL', lock_active=False)
+        self.assertEqual(self.cube.data.vertices[0].groups[0].weight, 0.75)
+        self.assertEqual(self.cube.data.vertices[0].groups[1].weight, 0.25)
+
+    def test_normalize_all_locked(self):
+        # Initial state.
+        self.cube.data.vertices[0].groups[0].weight = 0.375
+        self.cube.data.vertices[0].groups[1].weight = 0.125
+        self.cube.vertex_groups[0].lock_weight = True
+        self.cube.vertex_groups[1].lock_weight = True
+
+        # Attempt to normalize all vertex groups.  Should fail, leaving the weights as-is.
+        with self.assertRaises(RuntimeError):
+            bpy.ops.object.vertex_group_normalize_all(group_select_mode='ALL', lock_active=False)
+        self.assertEqual(self.cube.data.vertices[0].groups[0].weight, 0.375)
+        self.assertEqual(self.cube.data.vertices[0].groups[1].weight, 0.125)
+
+
+def main():
+    global args
+    import argparse
+
+    if '--' in sys.argv:
+        argv = [sys.argv[0]] + sys.argv[sys.argv.index('--') + 1:]
+    else:
+        argv = sys.argv
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--testdir', required=True, type=pathlib.Path)
+    args, remaining = parser.parse_known_args(argv)
+
+    unittest.main(argv=remaining)
+
+
+if __name__ == "__main__":
+    main()