[trac931] added a test case with the default keyring config.

also added a note in updateKeyring() about why we need to catch the case
of list==NULL explicitly.

src/lib/server_common/keyring.cc

@@ -30,6 +30,11 @@ void
 updateKeyring(const std::string&, ConstElementPtr data) {
     ConstElementPtr list(data->get("keys"));
     KeyringPtr load(new TSIGKeyRing);
+
+    // Note that 'data' only contains explicitly configured config parameters.
+    // So if we use the default list is NULL, rather than an empty list, and
+    // we must explicitly expect that case (and handle it just like an empty
+    // list).
     for (size_t i(0); list && i < list->size(); ++ i) {
         load->add(TSIGKey(list->get(i)->stringValue()));
     }

src/lib/server_common/tests/keyring_test.cc

@@ -43,15 +43,24 @@ public:
     isc::cc::FakeSession session;
     std::auto_ptr<ModuleCCSession> mccs;
     std::string specfile;
-    void doInit() {
+    void doInit(bool with_key = true) {
         // Prepare the module specification for it and the config
         session.getMessages()->
             add(createAnswer(0,
                              moduleSpecFromFile(std::string(PLUGIN_DATA_PATH) +
                                                 "/tsig_keys.spec").
                              getFullSpec()));
-        session.getMessages()->add(createAnswer(0, Element::fromJSON(
-            "{\"keys\": [\"key:MTIzNAo=:hmac-sha1\"]}")));
+        if (with_key) {
+            session.getMessages()->add(
+                createAnswer(0, Element::fromJSON(
+                                 "{\"keys\": [\"key:MTIzNAo=:hmac-sha1\"]}")));
+        } else {
+            // This emulates the case of using the spec default.  Note that
+            // the default value won't be passed to the config handler, so
+            // we'll pass an empty object, instead of {"keys": []}.
+            session.getMessages()->add(createAnswer(0,
+                                                    Element::fromJSON("{}")));
+        }
         // Now load it
         EXPECT_NO_THROW(initKeyring(*mccs));
         EXPECT_NE(keyring, boost::shared_ptr<TSIGKeyRing>()) <<
@@ -97,6 +106,14 @@ TEST_F(KeyringTest, keyring) {
     }
 }
 
+TEST_F(KeyringTest, keyringWithDefault) {
+    // If we don't explicitly specify a keyring, the default (no key) will
+    // be used.
+    doInit(false);
+    EXPECT_EQ(0, keyring->size());
+    deinitKeyring(*mccs);
+}
+
 // Init twice
 TEST_F(KeyringTest, initTwice) {
     // It is NULL before