diff --git a/tests/test_dict_state.py b/tests/test_dict_state.py
index 97fc054..9cdf721 100644
--- a/tests/test_dict_state.py
+++ b/tests/test_dict_state.py
@@ -35,3 +35,7 @@ def test_set(vector_state: VectorState) -> None:
     assert isinstance(vector_state.x, IntState) and vector_state.x.value == 1
     assert isinstance(vector_state.y, IntState) and vector_state.y.value == 2
     assert isinstance(vector_state.z, IntState) and vector_state.z.value == 3
+
+    vector_state.set(*[], y=IntState(10), z=5)
+    assert isinstance(vector_state.y, IntState) and vector_state.y.value == 10
+    assert isinstance(vector_state.z, IntState) and vector_state.z.value == 5
diff --git a/tests/test_higher_order_state.py b/tests/test_higher_order_state.py
index 3de8faa..02d2619 100644
--- a/tests/test_higher_order_state.py
+++ b/tests/test_higher_order_state.py
@@ -97,3 +97,15 @@ def test_deserialize(super_state: SuperState, callback: MockCallback) -> None:
 def test_to_str(super_state: SuperState) -> None:
     assert super_state.to_str() == _str
     assert str(super_state) == _str
+
+
+def test_copy_from(super_state: SuperState) -> None:
+    new_state = SuperState()
+    new_state.name.value = "Test"
+    new_state.count.value = 2
+    new_state.nested.length.value = 2.71
+
+    super_state.copy_from(new_state)
+    assert super_state.name.value == "Test"
+    assert super_state.count.value == 2
+    assert super_state.nested.length.value == 2.71
diff --git a/tests/test_list_state.py b/tests/test_list_state.py
index d3fb3dc..faa2926 100644
--- a/tests/test_list_state.py
+++ b/tests/test_list_state.py
@@ -164,3 +164,12 @@ def test_serialize(list_state: ListState) -> None:
 def test_deserialize(list_state: ListState) -> None:
     with pytest.raises(NotImplementedError):
         list_state.deserialize([0, 1, 2])
+
+
+def test_copy_from(list_state: ListState) -> None:
+    new_list: ListState[IntState] = ListState()
+    new_list.copy_from(list_state)
+
+    assert len(new_list) == len(list_state)
+    for i in range(len(new_list)):
+        assert new_list[i].value == list_state[i].value
diff --git a/tests/test_state.py b/tests/test_state.py
index f8a8e9d..e9f7f4a 100644
--- a/tests/test_state.py
+++ b/tests/test_state.py
@@ -76,3 +76,8 @@ def test_serialize(state: State) -> None:
 def test_deserialize(state: State) -> None:
     with pytest.raises(NotImplementedError):
         state.deserialize(0)
+
+
+def test_copy_from(state: State) -> None:
+    with pytest.raises(NotImplementedError):
+        state.copy_from(state)
diff --git a/widget_state/dict_state.py b/widget_state/dict_state.py
index 19bebdb..dfc2425 100644
--- a/widget_state/dict_state.py
+++ b/widget_state/dict_state.py
@@ -56,13 +56,13 @@ def values(self) -> list[Any]:
     def set(
         self,
         *args: BasicState[Any] | Primitive,
-        **kwargs: dict[str, BasicState[Any] | Primitive],
+        **kwargs: BasicState[Any] | Primitive,
     ) -> None:
         """
         Reassign internal basic state values and only
         trigger a notification afterwards.
         """
-        assert len(args) == len(self)
+        assert len(args) <= len(self)
 
         with self:
             for i, arg in enumerate(args):