test_state: add test_mutable_copy for entire state and mutable vars

Test case for #1841

tests/test_state.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import copy
 import datetime
 import functools
 import sys
@@ -1585,6 +1586,56 @@ def assert_custom_dirty():
     assert_custom_dirty()
 
 
+@pytest.mark.parametrize(
+    ("copy_func",),
+    [
+        (copy.copy,),
+        (copy.deepcopy,),
+    ],
+)
+def test_mutable_copy(mutable_state, copy_func):
+    """Test that mutable types are copied correctly.
+
+    Args:
+        mutable_state: A test state.
+        copy_func: A copy function.
+    """
+    ms_copy = copy_func(mutable_state)
+    assert ms_copy is not mutable_state
+    for attr in ("array", "hashmap", "test_set", "custom"):
+        assert getattr(ms_copy, attr) == getattr(mutable_state, attr)
+        assert getattr(ms_copy, attr) is not getattr(mutable_state, attr)
+    ms_copy.custom.array.append(42)
+    assert "custom" in ms_copy.dirty_vars
+    if copy_func is copy.copy:
+        assert "custom" in mutable_state.dirty_vars
+    else:
+        assert not mutable_state.dirty_vars
+
+
+@pytest.mark.parametrize(
+    ("copy_func",),
+    [
+        (copy.copy,),
+        (copy.deepcopy,),
+    ],
+)
+def test_mutable_copy_vars(mutable_state, copy_func):
+    """Test that mutable types are copied correctly.
+
+    Args:
+        mutable_state: A test state.
+        copy_func: A copy function.
+    """
+    for attr in ("array", "hashmap", "test_set", "custom"):
+        var_orig = getattr(mutable_state, attr)
+        var_copy = copy_func(var_orig)
+        assert var_orig is not var_copy
+        assert var_orig == var_copy
+        # copied vars should never be proxies, as they by definition are no longer attached to the state.
+        assert not isinstance(var_copy, MutableProxy)
+
+
 def test_duplicate_substate_class(duplicate_substate):
     with pytest.raises(ValueError):
         duplicate_substate()