diff --git a/tests/test_dns_utils.py b/tests/test_dns_utils.py
index 0772fce5..e8e9285f 100644
--- a/tests/test_dns_utils.py
+++ b/tests/test_dns_utils.py
@@ -38,3 +38,9 @@ def test_is_mx_equivalent():
     assert is_mx_equivalent(
         [(5, "domain1"), (10, "domain2")], [(10, "domain1"), (20, "domain2")]
     )
+    assert is_mx_equivalent(
+        [(5, "domain1"), (10, "domain2"), (20, "domain3")], [(10, "domain1"), (20, "domain2")]
+    )
+    assert not is_mx_equivalent(
+        [(5, "domain1"), (10, "domain2")], [(10, "domain1"), (20, "domain2"), (20, "domain3")]
+    )