diff --git a/python/tests/test_Grid.py b/python/tests/test_Grid.py
index 6dd94f4bb..c453b6c74 100644
--- a/python/tests/test_Grid.py
+++ b/python/tests/test_Grid.py
@@ -42,6 +42,10 @@ class TestGrid:
         print('patched datetime.datetime.now')
 
 
+    def test_show(sef,default,monkeypatch):
+        monkeypatch.delenv('DISPLAY',raising=False)
+        default.show()
+
     def test_equal(self,default):
         assert default == default
         assert not default == 42
diff --git a/python/tests/test_VTK.py b/python/tests/test_VTK.py
index 9613a483b..885c9bd95 100644
--- a/python/tests/test_VTK.py
+++ b/python/tests/test_VTK.py
@@ -1,6 +1,7 @@
 import os
 import filecmp
 import time
+import string
 
 import pytest
 import numpy as np
@@ -173,6 +174,22 @@ class TestVTK:
         assert str(mask_manual) == str(mask_auto)
 
 
+    @pytest.mark.parametrize('data_type,shape',[(float,(3,)),
+                                                (float,(3,3)),
+                                                (float,(1,)),
+                                                (int,(4,)),
+                                                (str,(1,))])
+    @pytest.mark.parametrize('N_values',[5*6*7,6*7*8])
+    def test_labels(self,default,data_type,shape,N_values):
+        data = np.squeeze(np.random.randint(0,100,(N_values,)+shape)).astype(data_type)
+        ALPHABET = np.array(list(string.ascii_lowercase + ' '))
+        label = ''.join(np.random.choice(ALPHABET, size=10))
+        new = default.add(data,label)
+        if N_values == default.N_points: assert label in new.labels['Point Data']
+        if N_values == default.N_cells:  assert label in new.labels['Cell Data']
+
+
+
     def test_comments(self,tmp_path,default):
         default.comments += 'this is a comment'
         default.save(tmp_path/'with_comments',parallel=False)