--- a
+++ b/tests/edgepy/test_stats.py
@@ -0,0 +1,31 @@
+import unittest
+
+from inmoose.edgepy import pnbinom, qnbinom
+
+
+class test_nbinom(unittest.TestCase):
+    def test_nbinom(self):
+        for i in range(10):
+            hi = pnbinom(i, size=5, prob=0.2, lower_tail=False)
+            lo = pnbinom(i, size=5, prob=0.2, lower_tail=True)
+            self.assertEqual(hi, 1.0 - lo)
+            self.assertEqual(i, qnbinom(hi, size=5, prob=0.2, lower_tail=False))
+            self.assertEqual(i, qnbinom(lo, size=5, prob=0.2, lower_tail=True))
+
+            hi = pnbinom(i, size=5, mu=4, lower_tail=False)
+            lo = pnbinom(i, size=5, mu=4, lower_tail=True)
+            self.assertAlmostEqual(hi, 1.0 - lo)
+            self.assertEqual(i, qnbinom(hi, size=5, mu=4, lower_tail=False))
+            self.assertEqual(i, qnbinom(lo, size=5, mu=4, lower_tail=True))
+
+        ctxt = self.assertRaisesRegex(
+            ValueError, expected_regex="exactly one of prob and mu must be provided"
+        )
+        with ctxt:
+            pnbinom(42, size=5, prob=0.5, mu=4)
+        with ctxt:
+            qnbinom(42, size=5, prob=0.5, mu=4)
+        with ctxt:
+            pnbinom(42, size=5)
+        with ctxt:
+            qnbinom(42, size=5)