Anim: Unit tests for "Insert Needed"

Add unit tests for the user preference option "Insert Needed"

Basic tests for objects and bones that check if autokeying in
combination with "Insert Needed" only
* keys all location channels on the first key
* keys only the modified channel on the second key

It is supposed to add only keyframes that have been affected
by the used transform operation.
E.g. translating an object will only add keys on translation keys.

The behavior of keying all property array channels first, and then
only add keys on values that have actually changed may change
in the future. Ideally it would only key actual changes to begin
with. But there is no way to do this right now.

Pull Request: https://projects.blender.org/blender/blender/pulls/116419

tests/python/bl_animation_keyframing.py

@@ -395,6 +395,75 @@ class InsertAvailableTest(AbstractKeyframingTest, unittest.TestCase):
         bpy.data.objects.remove(keyed_object, do_unlink=True)
 
 
+class InsertNeededTest(AbstractKeyframingTest, unittest.TestCase):
+
+    def setUp(self):
+        super().setUp()
+        bpy.context.scene.tool_settings.use_keyframe_insert_auto = True
+        bpy.context.preferences.edit.use_keyframe_insert_needed = True
+        bpy.context.preferences.edit.use_keyframe_insert_available = False
+
+    def tearDown(self):
+        bpy.context.scene.tool_settings.use_keyframe_insert_auto = False
+        bpy.context.preferences.edit.use_keyframe_insert_needed = False
+
+    def test_insert_needed_object(self):
+        keyed_object = _create_animation_object()
+
+        with bpy.context.temp_override(**_get_view3d_context()):
+            bpy.context.scene.frame_set(1)
+            bpy.ops.transform.translate(value=(-1, 0, 0))
+            bpy.context.scene.frame_set(5)
+            bpy.ops.transform.translate(value=(1, 0, 0))
+
+        action = keyed_object.animation_data.action
+        self.assertTrue(_fcurve_paths_match(action.fcurves, ["location"]))
+
+        # With "Insert Needed" enabled it has to key all location channels first,
+        # before it can add keys only to the channels where values have actually
+        # changed.
+        expected_keys = {
+            "location": (2, 1, 1)
+        }
+
+        self.assertEqual(len(action.fcurves), 3)
+
+        for fcurve in action.fcurves:
+            if fcurve.data_path not in expected_keys:
+                raise AssertionError(f"Did not expect a key on {fcurve.data_path}")
+            self.assertEqual(expected_keys[fcurve.data_path][fcurve.array_index], len(fcurve.keyframe_points))
+
+    def test_insert_needed_bone(self):
+        armature_obj = _create_armature()
+
+        bpy.ops.object.mode_set(mode='POSE')
+        with bpy.context.temp_override(**_get_view3d_context()):
+            bpy.context.scene.frame_set(1)
+            bpy.ops.transform.translate(value=(-1, 0, 0), orient_type='LOCAL')
+            bpy.context.scene.frame_set(5)
+            bpy.ops.transform.translate(value=(1, 0, 0), orient_type='LOCAL')
+
+        bpy.ops.object.mode_set(mode='OBJECT')
+
+        action = armature_obj.animation_data.action
+        bone_path = f"pose.bones[\"{_BONE_NAME}\"]"
+        self.assertTrue(_fcurve_paths_match(action.fcurves, [f"{bone_path}.location"]))
+
+        # With "Insert Needed" enabled it has to key all location channels first,
+        # before it can add keys only to the channels where values have actually
+        # changed.
+        expected_keys = {
+            f"{bone_path}.location": (2, 1, 1)
+        }
+
+        self.assertEqual(len(action.fcurves), 3)
+
+        for fcurve in action.fcurves:
+            if fcurve.data_path not in expected_keys:
+                raise AssertionError(f"Did not expect a key on {fcurve.data_path}")
+            self.assertEqual(expected_keys[fcurve.data_path][fcurve.array_index], len(fcurve.keyframe_points))
+
+
 def main():
     global args
     import argparse