diff --git a/python/tests/test_Geom.py b/python/tests/test_Geom.py
index 68d727f11..1639d9819 100644
--- a/python/tests/test_Geom.py
+++ b/python/tests/test_Geom.py
@@ -171,6 +171,10 @@ class TestGeom:
     def test_flip_invariant(self,default):
         assert geom_equal(default,default.flip([]))
 
+    @pytest.mark.parametrize('direction',[['x'],['x','y']])
+    def test_flip_double(self,default,direction):
+        assert geom_equal(default,default.flip(direction).flip(direction))
+
     @pytest.mark.parametrize('directions',[(1,2,'y'),('a','b','x'),[1]])
     def test_flip_invalid(self,default,directions):
         with pytest.raises(ValueError):
diff --git a/python/tests/test_VTK.py b/python/tests/test_VTK.py
index 35155caa2..ab9c4fa8b 100644
--- a/python/tests/test_VTK.py
+++ b/python/tests/test_VTK.py
@@ -100,15 +100,18 @@ class TestVTK:
         with pytest.raises(ValueError):
             default.get('does_not_exist')
 
-    @pytest.mark.parametrize('data,label',[(np.ones(3),'valid'),
-                                           (np.ones(3),None)])
-    def test_invalid_add(self,default,data,label):
+    def test_invalid_add_shape(self,default):
         with pytest.raises(ValueError):
-            default.add(np.ones(3),label)
+            default.add(np.ones(3),'valid')
+
+    def test_invalid_add_missing_label(self,default):
+        data = np.random.randint(9,size=np.prod(np.array(default.vtk_data.GetDimensions())-1))
+        with pytest.raises(ValueError):
+            default.add(data)
 
     def test_invalid_add_type(self,default):
         with pytest.raises(TypeError):
-            default.add('invalid_type','label')
+            default.add('invalid_type','valid')
 
     def test_comments(self,tmp_path,default):
         default.add_comments(['this is a comment'])
@@ -116,7 +119,6 @@ class TestVTK:
         new = VTK.from_file(tmp_path/'with_comments.vtr')
         assert new.get_comments() == ['this is a comment']
 
-
     def test_compare_reference_polyData(self,update,reference_dir,tmp_path):
         points=np.dstack((np.linspace(0.,1.,10),np.linspace(0.,2.,10),np.linspace(-1.,1.,10))).squeeze()
         polyData = VTK.from_polyData(points)