Add tests for verify callback
As we're about to change the chain construction logic, we want to make sure
the callback will still be called exactly when it should, and not on the
(upcoming) ignored certs in the chain.
diff --git a/tests/data_files/server10.key b/tests/data_files/server10.key
new file mode 100644
index 0000000..0088331
--- /dev/null
+++ b/tests/data_files/server10.key
@@ -0,0 +1,5 @@
+-----BEGIN EC PRIVATE KEY-----
+MHcCAQEEILBDMs7bRVxVg6ovTpf2zB9m+22jY7R3LNKRvCPfa6YJoAoGCCqGSM49
+AwEHoUQDQgAEHG336dql6qGcsnIZqAkcc63eFbvepuOzTwXobRAuOmk3l4A5wXX/
+vs5wAawLX1wUTUM/AESHmAZrJK9tq5So8g==
+-----END EC PRIVATE KEY-----