diff --git a/biometrics/cluster.py b/biometrics/cluster.py
index 9d7f0e3..8dae9db 100644
--- a/biometrics/cluster.py
+++ b/biometrics/cluster.py
@@ -44,7 +44,7 @@ def cluster(self, comparisons):
             max_occurence = occurences.most_common()
             max_occurence_val = max_occurence[0][1]
             most_common_group = list(filter(lambda x: x[1] == max_occurence_val, max_occurence))
-            most_common_group = ','.join([i[0] for i in most_common_group])
+            most_common_group = ':'.join([i[0] for i in most_common_group])
 
             for i, sample in enumerate(samples_in_group):
 
diff --git a/requirements.txt b/requirements.txt
index d250250..8c58cc5 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,8 +2,8 @@ networkx
 numpy
 pandas
 plotly
-pysam==0.16.0.1
-PyVCF==0.6.8
+pysam
+pyvcf3
 python-dateutil
 pytz
 retrying
diff --git a/tests/test_data/test_sample1.pickle b/tests/test_data/test_sample1.pickle
new file mode 100644
index 0000000..adc374f
Binary files /dev/null and b/tests/test_data/test_sample1.pickle differ
diff --git a/tests/test_data/test_sample2.pickle b/tests/test_data/test_sample2.pickle
new file mode 100644
index 0000000..0ecb7c6
Binary files /dev/null and b/tests/test_data/test_sample2.pickle differ