improve the robustness of ndncert library

Change-Id: Iaabc4d8f28ca27a7e7f501ebd122c5231ceb3ac0
diff --git a/tests/unit-tests/ca.conf.test2 b/tests/unit-tests/ca.conf.test2
new file mode 100644
index 0000000..17f058b
--- /dev/null
+++ b/tests/unit-tests/ca.conf.test2
@@ -0,0 +1,9 @@
+{
+  "issuing-freshness": "720",
+  "validity-period": "360",
+  "ca-info": "ndn testbed ca",
+  "supported-challenges":
+  [
+      { "type": "PIN" }
+  ]
+}
\ No newline at end of file