--- a/tests/test-rust-ancestor.py	Mon Jan 14 18:52:01 2019 +0100
+++ b/tests/test-rust-ancestor.py	Mon Jan 14 17:07:39 2019 +0100
@@ -114,6 +114,7 @@
         missanc.addbases({2})
         self.assertEqual(missanc.bases(), {1, 2})
         self.assertEqual(missanc.missingancestors([3]), [3])
+        self.assertEqual(missanc.basesheads(), {2})
 
     def testmissingancestorsremove(self):
         idx = self.parseindex()