diff --git a/tests/tests.py b/tests/tests.py
index 273051e..53b2764 100644
--- a/tests/tests.py
+++ b/tests/tests.py
@@ -6,15 +6,26 @@ from pymispgalaxies import Galaxies, Clusters, UnableToRevertMachinetag
 from glob import glob
 import os
 import json
+from collections import Counter
 
 
 class TestPyMISPGalaxies(unittest.TestCase):
 
     def setUp(self):
         self.galaxies = Galaxies()
-        self.clusters = Clusters()
+        self.clusters = Clusters(skip_duplicates=True)
         self.maxDiff = None
 
+    def test_duplicates(self):
+        has_duplicates = False
+        for name, c in self.clusters.items():
+            if c.duplicates:
+                has_duplicates = True
+                to_print = Counter(c.duplicates)
+                for entry, counter in to_print.items():
+                    print(counter + 1, entry)
+        self.assertFalse(has_duplicates)
+
     def test_dump_galaxies(self):
         galaxies_from_files = {}
         for galaxy_file in glob(os.path.join(self.galaxies.root_dir_galaxies, '*.json')):