consolidate dsa serialization loading tests and improve verifier
diff --git a/tests/hazmat/primitives/utils.py b/tests/hazmat/primitives/utils.py
index 0c9af50..e148bc6 100644
--- a/tests/hazmat/primitives/utils.py
+++ b/tests/hazmat/primitives/utils.py
@@ -414,3 +414,10 @@
     assert skey.dmp1 == rsa.rsa_crt_dmp1(skey.d, skey.p)
     assert skey.dmq1 == rsa.rsa_crt_dmq1(skey.d, skey.q)
     assert skey.iqmp == rsa.rsa_crt_iqmp(skey.p, skey.q)
+
+
+def _check_dsa_private_numbers(skey):
+    assert skey
+    pkey = skey.public_numbers
+    params = pkey.parameter_numbers
+    assert pow(params.g, skey.x, params.p) == pkey.y