[trac704] Add tests to check that RTT can's be set to 0

... and a test to check that setting the RTT to an absurdly high
value causes no problems.

src/lib/nsas/tests/nameserver_entry_unittest.cc

@@ -513,6 +513,11 @@ TEST_F(NameserverEntryTest, UpdateRTT) {
 
     // The rtt should be close to stable rtt value
     EXPECT_TRUE((stable_rtt - new_rtt) < (new_rtt - init_rtt));
+
+    // Finally, try updating the RTT to a very large value (large enough for
+    // RTT^2 - used in the internal calculation - to exceed a 32-bit value).
+    EXPECT_NO_THROW(vec[0].updateRTT(1000000000));  // 10^9
+
 }
 
 }   // namespace

src/lib/nsas/tests/nsas_test.h

@@ -320,20 +320,26 @@ class TestResolver : public isc::resolve::ResolverInterface {
 
         /*
          * Sends a simple answer to a query.
-         * Provide index of a query and the address to pass.
+         * 1) Provide index of a query and the address(es) to pass.
+         * 2) Provide index of query and components of address to pass.
          */
-        void answer(size_t index, const Name& name, const RRType& type,
-            const rdata::Rdata& rdata, size_t TTL = 100)
-        {
+        void answer(size_t index, RRsetPtr& set) {
             if (index >= requests.size()) {
                 throw NoSuchRequest();
             }
+            requests[index].second->success(createResponseMessage(set));
+        }
+
+        void answer(size_t index, const Name& name, const RRType& type,
+            const rdata::Rdata& rdata, size_t TTL = 100)
+        {
             RRsetPtr set(new RRset(name, RRClass::IN(),
                 type, RRTTL(TTL)));
             set->addRdata(rdata);
-            requests[index].second->success(createResponseMessage(set));
+            answer(index, set);
         }
 
+
         void provideNS(size_t index,
             RRsetPtr nameservers)
         {