[trac661] Update the comments in test data file

src/lib/cache/tests/rrset_cache_unittest.cc

@@ -74,7 +74,7 @@ TEST_F(RRsetCacheTest, lookup) {
     // Check whether the expired rrset entry will be removed automatically
     // when looking up.
     Name name_test("test.example.com.");
-    updateRRsetCache(cache_, name_test, 0);
+    updateRRsetCache(cache_, name_test, 0); // Add a rrset with TTL 0 to cache.
     EXPECT_FALSE(cache_.lookup(name_test, RRType::A()));
 }
 

src/lib/cache/tests/testdata/message_fromWire9

@@ -1,4 +1,6 @@
 #
+# The TTL for a record in answer section is 0, so it
+# will expire immediately after being cached.
 #
 # A simple DNS response message
 # ID = 0x1035
@@ -6,7 +8,7 @@
 # QDCOUNT=1, ANCOUNT=2, other COUNTS=0
 # Question: test.example.org. IN A
 # Answer:
-#  test.example.org. 3600 IN A 192.0.2.1
+#  test.example.org. 0000 IN A 192.0.2.1
 #  test.example.org. 7200 IN A 192.0.2.2
 #
 1035 8500