add unit test for ReplacementTransform

Author: irvanalhaq9

tests/module/animation/test_transform.py

@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+from manim import Circle, ReplacementTransform, Scene, Square, VGroup
+
+
+def test_no_duplicate_references():
+    scene = Scene()
+    c = Circle()
+    sq = Square()
+    scene.add(c, sq)
+
+    scene.play(ReplacementTransform(c, sq))
+    assert len(scene.mobjects) == 1
+    assert scene.mobjects[0] is sq
+
+
+def test_duplicate_references_in_group():
+    scene = Scene()
+    c = Circle()
+    sq = Square()
+    vg = VGroup(c, sq)
+    scene.add(vg)
+
+    scene.play(ReplacementTransform(c, sq))
+    submobs = vg.submobjects
+    assert len(submobs) == 1
+    assert submobs[0] is sq