test: Add initial unit tests for c-ares library

The tests are written in C++11, using the GoogleTest and GoogleMock frameworks. They have their own independent autoconf setup, so that users of the library need not have a C++ compiler just to get c-ares working (however, the test/configure.ac file does assume the use of a shared top-level m4/ directory). However, this autoconf setup has only been tested on Linux and OSX so far. Run with "./arestest", or "./arestest -v" to see extra debug info. The GoogleTest options for running specific tests are also available (e.g. "./arestest --gtest_filter=*Live*"). The tests are nowhere near complete yet (currently hitting around 60% coverage as reported by gcov), but they do include examples of a few different styles of testing: - There are live tests (ares-test-live.cc), which assume that the current machine has a valid DNS setup and connection to the internet; these tests issue queries for real domains but don't particularly check what gets returned. The tests will fail on an offline machine. - There a few mock tests (ares-test-mock.cc) that set up a fake DNS server and inject its port into the c-ares library configuration. These tests allow specific response messages to be crafted and injected, and so are likely to be used for many more tests in future. - To make this generation/injection easier, the dns-proto.h file includes C++ helper classes for building DNS packets. - Other library entrypoints that don't require network activity (e.g. ares_parse_*_reply) are tested directly. - There are few tests of library-internal functions that are not normally visible to API users (in ares-test-internal.cc). - A couple of the tests use a helper method of the test fixture to inject memory allocation failures, using the earlier change to the library to allow override of malloc/realloc/free. - There is also an entrypoint to allow Clang's libfuzzer to drive the packet parsing code in ares_parse_*_reply, together with a standalone wrapper for it (./aresfuzz) to allow use of afl-fuzz for further fuzz testing.
9 years ago · af3ee9a8ba
parent 148b6e93b9
commit af3ee9a8ba
20 changed files with 2918 additions and 0 deletions
--- a/test/.gitignore
+++ b/test/.gitignore
@ -0,0 +1,9 @@
+*.o
+libgtest.a
+libgmock.a
+arestest
+aresfuzz
+arestest.log
+arestest.trs
+test-suite.log
+fuzzoutput
--- a/test/Makefile.am
+++ b/test/Makefile.am
@ -0,0 +1,33 @@
+# Where to find the c-ares source code; needed because the tests use library-internal headers
+ARES_SRC_DIR = ..
+# Where to find the built c-ares static library
+ARES_BLD_DIR = ..
+AUTOMAKE_OPTIONS = foreign
+ACLOCAL_AMFLAGS = -I ../m4
+GMOCK_DIR = gmock-1.7.0
+GTEST_DIR = $(GMOCK_DIR)/gtest
+# Note use of -isystem to force use of local gMock/gTest even if there's an installed version.
+CPPFLAGS += -I$(ARES_SRC_DIR) -isystem $(GTEST_DIR)/include -isystem $(GMOCK_DIR)/include
+CXXFLAGS += -Wall --std=c++11 -g $(PTHREAD_CFLAGS)
+
+TESTS = arestest
+
+noinst_PROGRAMS = arestest aresfuzz
+arestest_SOURCES = ares-test-main.cc ares-test-init.cc ares-test.cc ares-test-parse.cc ares-test-misc.cc ares-test-live.cc ares-test-mock.cc ares-test-internal.cc dns-proto.cc dns-proto-test.cc ares-test.h dns-proto.h
+arestest_LDADD = libgmock.la libgtest.la $(ARES_BLD_DIR)/libcares.la $(PTHREAD_LIBS)
+
+# Not interested in coverage of test code, but linking the test binary needs the coverage option
+@CODE_COVERAGE_RULES@
+arestest_LDFLAGS = $(CODE_COVERAGE_LDFLAGS)
+
+noinst_LTLIBRARIES = libgmock.la libgtest.la
+
+libgmock_la_SOURCES = $(GMOCK_DIR)/src/gmock-all.cc
+libgmock_la_CPPFLAGS = -isystem $(GTEST_DIR)/include -I$(GTEST_DIR) -isystem $(GMOCK_DIR)/include -I$(GMOCK_DIR)
+libgtest_la_SOURCES = $(GTEST_DIR)/src/gtest-all.cc
+libgtest_la_CPPFLAGS = -isystem $(GTEST_DIR)/include -I$(GTEST_DIR) -isystem $(GMOCK_DIR)/include -I$(GMOCK_DIR)
+
+aresfuzz_SOURCES = ares-test-fuzz.cc ares-fuzz.cc
+aresfuzz_LDADD = $(ARES_BLD_DIR)/libcares.la
+
+test: check
--- a/test/ares-fuzz.cc
+++ b/test/ares-fuzz.cc
@ -0,0 +1,20 @@
+// General driver to allow command-line fuzzer (i.e. afl) to
+// fuzz the libfuzzer entrypoint.
+#include <stdio.h>
+#include <unistd.h>
+
+#include <vector>
+
+extern "C" void LLVMFuzzerTestOneInput(const unsigned char *data,
+                                       unsigned long size);
+int main() {
+  std::vector<unsigned char> input;
+  while (true) {
+    unsigned char buffer[1024];
+    int len = read(fileno(stdin), buffer, sizeof(buffer));
+    if (len <= 0) break;
+    input.insert(input.end(), buffer, buffer + len);
+  }
+  LLVMFuzzerTestOneInput(input.data(), input.size());
+  return 0;
+}
--- a/test/ares-test-fuzz.cc
+++ b/test/ares-test-fuzz.cc
@ -0,0 +1,44 @@
+#include "ares-test.h"
+#include <vector>
+
+// Entrypoint for Clang's libfuzzer
+extern "C" void LLVMFuzzerTestOneInput(const unsigned char *data,
+                                       unsigned long size) {
+  // Feed the data into each of the ares_parse_*_reply functions.
+  struct hostent *host = nullptr;
+  struct ares_addrttl info[5];
+  int count = 5;
+  ares_parse_a_reply(data, size, &host, info, &count);
+  if (host) ares_free_hostent(host);
+
+  host = nullptr;
+  struct ares_addr6ttl info6[5];
+  count = 5;
+  ares_parse_aaaa_reply(data, size, &host, info6, &count);
+  if (host) ares_free_hostent(host);
+
+  host = nullptr;
+  ares::byte addrv4[4] = {0x10, 0x20, 0x30, 0x40};
+  ares_parse_ptr_reply(data, size, addrv4, sizeof(addrv4), AF_INET, &host);
+  if (host) ares_free_hostent(host);
+
+  host = nullptr;
+  ares_parse_ns_reply(data, size, &host);
+  if (host) ares_free_hostent(host);
+
+  struct ares_srv_reply* srv = nullptr;
+  ares_parse_srv_reply(data, size, &srv);
+  if (srv) ares_free_data(srv);
+
+  struct ares_mx_reply* mx = nullptr;
+  ares_parse_mx_reply(data, size, &mx);
+  if (mx) ares_free_data(mx);
+
+  struct ares_txt_reply* txt = nullptr;
+  ares_parse_txt_reply(data, size, &txt);
+  if (txt) ares_free_data(txt);
+
+  struct ares_soa_reply* soa = nullptr;
+  ares_parse_soa_reply(data, size, &soa);
+  if (soa) ares_free_data(soa);
+}
--- a/test/ares-test-init.cc
+++ b/test/ares-test-init.cc
@ -0,0 +1,71 @@
+
+#include "ares-test.h"
+
+// library initialization is only needed for windows builds
+#ifdef USE_WINSOCK
+#define EXPECTED_NONINIT ARES_ENOTINITIALIZED
+#else
+#define EXPECTED_NONINIT ARES_SUCCESS
+#endif
+
+namespace ares {
+namespace test {
+
+TEST(LibraryInit, Basic) {
+  EXPECT_EQ(EXPECTED_NONINIT, ares_library_initialized());
+  EXPECT_EQ(ARES_SUCCESS, ares_library_init(ARES_LIB_INIT_ALL));
+  EXPECT_EQ(ARES_SUCCESS, ares_library_initialized());
+  ares_library_cleanup();
+  EXPECT_EQ(EXPECTED_NONINIT, ares_library_initialized());
+}
+
+TEST(LibraryInit, DISABLED_InvalidParam) {
+  // TODO: police flags argument to ares_library_init()
+  EXPECT_EQ(ARES_EBADQUERY, ares_library_init(ARES_LIB_INIT_ALL << 2));
+  EXPECT_EQ(EXPECTED_NONINIT, ares_library_initialized());
+  ares_library_cleanup();
+}
+
+TEST(LibraryInit, Nested) {
+  EXPECT_EQ(EXPECTED_NONINIT, ares_library_initialized());
+  EXPECT_EQ(ARES_SUCCESS, ares_library_init(ARES_LIB_INIT_ALL));
+  EXPECT_EQ(ARES_SUCCESS, ares_library_initialized());
+  EXPECT_EQ(ARES_SUCCESS, ares_library_init(ARES_LIB_INIT_ALL));
+  EXPECT_EQ(ARES_SUCCESS, ares_library_initialized());
+  ares_library_cleanup();
+  EXPECT_EQ(ARES_SUCCESS, ares_library_initialized());
+  ares_library_cleanup();
+  EXPECT_EQ(EXPECTED_NONINIT, ares_library_initialized());
+}
+
+TEST_F(LibraryTest, BasicChannelInit) {
+  EXPECT_EQ(ARES_SUCCESS, ares_library_init(ARES_LIB_INIT_ALL));
+  ares_channel channel = nullptr;
+  EXPECT_EQ(ARES_SUCCESS, ares_init(&channel));
+  EXPECT_NE(nullptr, channel);
+  ares_destroy(channel);
+  ares_library_cleanup();
+}
+
+TEST_F(LibraryTest, FailChannelInit) {
+  EXPECT_EQ(ARES_SUCCESS,
+            ares_library_init_mem(ARES_LIB_INIT_ALL,
+                                  &LibraryTest::amalloc,
+                                  &LibraryTest::afree,
+                                  &LibraryTest::arealloc));
+  SetAllocFail(1);
+  ares_channel channel = nullptr;
+  EXPECT_EQ(ARES_ENOMEM, ares_init(&channel));
+  EXPECT_EQ(nullptr, channel);
+  ares_library_cleanup();
+}
+
+#ifdef USE_WINSOCK
+TEST(Init, NoLibraryInit) {
+  ares_channel channel = nullptr;
+  EXPECT_EQ(ARES_ENOTINITIALIZED, ares_init(&channel));
+}
+#endif
+
+}  // namespace test
+}  // namespace ares
--- a/test/ares-test-internal.cc
+++ b/test/ares-test-internal.cc
@ -0,0 +1,56 @@
+#include "ares-test.h"
+#include "dns-proto.h"
+
+extern "C" {
+#include "ares_nowarn.h"
+#include "ares_inet_net_pton.h"
+#include "bitncmp.h"
+}
+
+#include <string>
+#include <vector>
+
+namespace ares {
+namespace test {
+
+TEST_F(LibraryTest, InetPtoN) {
+  struct in_addr a4;
+  struct in6_addr a6;
+#ifdef DISABLED
+  EXPECT_EQ(1, ares_inet_net_pton(AF_INET, "1.2.3.4", &a4, sizeof(a4)));
+  EXPECT_EQ(1, ares_inet_net_pton(AF_INET6, "12:34::ff", &a6, sizeof(a6)));
+  EXPECT_EQ(1, ares_inet_net_pton(AF_INET6, "12:34::ffff:1.2.3.4", &a6, sizeof(a6)));
+  EXPECT_EQ(0, ares_inet_net_pton(AF_INET, "xyzzy", &a4, sizeof(a4)));
+  EXPECT_EQ(-1, ares_inet_net_pton(AF_INET+AF_INET6, "1.2.3.4", &a4, sizeof(a4)));
+#endif
+  EXPECT_EQ(1, ares_inet_pton(AF_INET, "1.2.3.4", &a4));
+  EXPECT_EQ(1, ares_inet_pton(AF_INET6, "12:34::ff", &a6));
+  EXPECT_EQ(1, ares_inet_pton(AF_INET6, "12:34::ffff:1.2.3.4", &a6));
+  EXPECT_EQ(0, ares_inet_pton(AF_INET, "xyzzy", &a4));
+  EXPECT_EQ(-1, ares_inet_pton(AF_INET+AF_INET6, "1.2.3.4", &a4));
+}
+
+#ifdef DISABLED
+TEST(Misc, Bitncmp) {
+  byte a[4] = {0x80, 0x01, 0x02, 0x03};
+  byte b[4] = {0x80, 0x01, 0x02, 0x04};
+  EXPECT_EQ(-1, ares__bitncmp(a, b, sizeof(a)*8));
+  EXPECT_EQ(1, ares__bitncmp(b, a, sizeof(a)*8));
+  EXPECT_EQ(0, ares__bitncmp(a, a, sizeof(a)*8));
+}
+
+TEST_F(LibraryTest, Casts) {
+  ssize_t ssz = 100;
+  unsigned int u = 100;
+  int i = 100;
+
+  unsigned int ru = aresx_sztoui(ssz);
+  EXPECT_EQ(u, ru);
+  int ri = aresx_sztosi(ssz);
+  EXPECT_EQ(i, ri);
+}
+#endif
+
+
+}  // namespace test
+}  // namespace ares
--- a/test/ares-test-live.cc
+++ b/test/ares-test-live.cc
@ -0,0 +1,121 @@
+// This file includes tests that attempt to do real lookups
+// of DNS names using the local machine's live infrastructure.
+
+#include "ares-test.h"
+
+#include <netdb.h>
+
+namespace ares {
+namespace test {
+
+TEST_F(DefaultChannelTest, LiveGetHostByNameV4) {
+  HostResult result;
+  ares_gethostbyname(channel_, "www.google.com.", AF_INET, HostCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+  EXPECT_LT(0, (int)result.host_.addrs_.size());
+  EXPECT_EQ(AF_INET, result.host_.addrtype_);
+}
+
+TEST_F(DefaultChannelTest, LiveGetHostByNameV6) {
+  HostResult result;
+  ares_gethostbyname(channel_, "www.google.com.", AF_INET6, HostCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+  EXPECT_LT(0, (int)result.host_.addrs_.size());
+  EXPECT_EQ(AF_INET6, result.host_.addrtype_);
+}
+
+TEST_F(DefaultChannelTest, LiveGetHostByAddrV4) {
+  HostResult result;
+  unsigned char addr[4] = {8, 8, 8, 8};
+  ares_gethostbyaddr(channel_, addr, sizeof(addr), AF_INET, HostCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+  EXPECT_LT(0, (int)result.host_.addrs_.size());
+  EXPECT_EQ(AF_INET, result.host_.addrtype_);
+}
+
+TEST_F(DefaultChannelTest, LiveGetHostByAddrV6) {
+  HostResult result;
+  unsigned char addr[16] = {0x20, 0x01, 0x48, 0x60, 0x48, 0x60, 0x00, 0x00,
+                            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x88, 0x88};
+  ares_gethostbyaddr(channel_, addr, sizeof(addr), AF_INET6, HostCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+  EXPECT_LT(0, (int)result.host_.addrs_.size());
+  EXPECT_EQ(AF_INET6, result.host_.addrtype_);
+}
+
+TEST_F(DefaultChannelTest, LiveSearchA) {
+  SearchResult result;
+  ares_search(channel_, "www.facebook.com.", ns_c_in, ns_t_a,
+              SearchCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+}
+
+TEST_F(DefaultChannelTest, LiveSearchNS) {
+  SearchResult result;
+  ares_search(channel_, "google.com.", ns_c_in, ns_t_ns,
+              SearchCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+}
+
+TEST_F(DefaultChannelTest, LiveSearchMX) {
+  SearchResult result;
+  ares_search(channel_, "google.com.", ns_c_in, ns_t_mx,
+              SearchCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+}
+
+TEST_F(DefaultChannelTest, LiveSearchTXT) {
+  SearchResult result;
+  ares_search(channel_, "google.com.", ns_c_in, ns_t_txt,
+              SearchCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+}
+
+TEST_F(DefaultChannelTest, LiveSearchSOA) {
+  SearchResult result;
+  ares_search(channel_, "google.com.", ns_c_in, ns_t_soa,
+              SearchCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+}
+
+TEST_F(DefaultChannelTest, LiveSearchANY) {
+  SearchResult result;
+  ares_search(channel_, "facebook.com.", ns_c_in, ns_t_any,
+              SearchCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+}
+
+TEST_F(DefaultChannelTest, LiveGetNameInfo) {
+  NameInfoResult result;
+  struct sockaddr_in sockaddr;
+  memset(&sockaddr, 0, sizeof(sockaddr));
+  sockaddr.sin_family = AF_INET;
+  sockaddr.sin_port = htons(53);
+  sockaddr.sin_addr.s_addr = htonl(0x08080808);
+  ares_getnameinfo(channel_, (const struct sockaddr*)&sockaddr, sizeof(sockaddr),
+                   ARES_NI_LOOKUPHOST|ARES_NI_LOOKUPSERVICE|ARES_NI_UDP,
+                   NameInfoCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+
+CARES_EXTERN void ares_getnameinfo(ares_channel channel,
+                                   const struct sockaddr *sa,
+                                   ares_socklen_t salen,
+                                   int flags,
+                                   ares_nameinfo_callback callback,
+                                   void *arg);
+
+}
+
+}  // namespace test
+}  // namespace ares
--- a/test/ares-test-main.cc
+++ b/test/ares-test-main.cc
@ -0,0 +1,19 @@
+#include <sys/types.h>
+#include <ctype.h>
+#include <errno.h>
+#include <pwd.h>
+#include <iostream>
+
+#include "ares-test.h"
+
+int main(int argc, char* argv[]) {
+  ::testing::InitGoogleTest(&argc, argv);
+  for (int ii = 1; ii < argc; ii++) {
+    if (strcmp(argv[ii], "-v") == 0) {
+      ares::test::verbose = true;
+    }
+  }
+
+  int rc = RUN_ALL_TESTS();
+  return rc;
+}
--- a/test/ares-test-misc.cc
+++ b/test/ares-test-misc.cc
@ -0,0 +1,222 @@
+#include "ares-test.h"
+#include "dns-proto.h"
+
+#include <string>
+#include <vector>
+
+namespace ares {
+namespace test {
+
+std::vector<std::string> GetNameServers(ares_channel channel) {
+  struct ares_addr_node* servers = nullptr;
+  EXPECT_EQ(ARES_SUCCESS, ares_get_servers(channel, &servers));
+  struct ares_addr_node* server = servers;
+  std::vector<std::string> results;
+  while (server) {
+    switch (server->family) {
+    case AF_INET:
+      results.push_back(AddressToString((char*)&server->addr.addr4, 4));
+      break;
+    case AF_INET6:
+      results.push_back(AddressToString((char*)&server->addr.addr6, 16));
+      break;
+    default:
+      results.push_back("<unknown family>");
+      break;
+    }
+    server = server->next;
+  }
+  ares_free_data(servers);
+  return results;
+}
+
+TEST_F(DefaultChannelTest, GetServers) {
+  std::vector<std::string> servers = GetNameServers(channel_);
+  if (verbose) {
+    for (const std::string& server : servers) {
+      std::cerr << "Nameserver: " << server << std::endl;
+    }
+  }
+}
+
+TEST_F(DefaultChannelTest, SetServers) {
+  EXPECT_EQ(ARES_SUCCESS, ares_set_servers(channel_, nullptr));
+  std::vector<std::string> empty;
+  EXPECT_EQ(empty, GetNameServers(channel_));
+
+  struct ares_addr_node server1;
+  struct ares_addr_node server2;
+  server1.next = &server2;
+  server1.family = AF_INET;
+  server1.addr.addr4.s_addr = htonl(0x01020304);
+  server2.next = nullptr;
+  server2.family = AF_INET;
+  server2.addr.addr4.s_addr = htonl(0x02030405);
+  EXPECT_EQ(ARES_ENODATA, ares_set_servers(nullptr, &server1));
+
+  EXPECT_EQ(ARES_SUCCESS, ares_set_servers(channel_, &server1));
+  std::vector<std::string> expected = {"1.2.3.4", "2.3.4.5"};
+  EXPECT_EQ(expected, GetNameServers(channel_));
+}
+
+TEST_F(DefaultChannelTest, SetServersCSV) {
+  EXPECT_EQ(ARES_ENODATA, ares_set_servers_csv(nullptr, "1.2.3.4"));
+  EXPECT_EQ(ARES_ENODATA, ares_set_servers_csv(nullptr, "xyzzy,plugh"));
+  EXPECT_EQ(ARES_ENODATA, ares_set_servers_csv(nullptr, "256.1.2.3"));
+  EXPECT_EQ(ARES_ENODATA, ares_set_servers_csv(nullptr, "1.2.3.4.5"));
+  EXPECT_EQ(ARES_ENODATA, ares_set_servers_csv(nullptr, "1:2:3:4:5"));
+
+  EXPECT_EQ(ARES_SUCCESS,
+            ares_set_servers_csv(channel_, "1.2.3.4,0102:0304:0506:0708:0910:1112:1314:1516,2.3.4.5"));
+  std::vector<std::string> expected = {"1.2.3.4", "0102:0304:0506:0708:0910:1112:1314:1516", "2.3.4.5"};
+  EXPECT_EQ(expected, GetNameServers(channel_));
+
+  // Same, with spaces
+  EXPECT_EQ(ARES_EBADSTR,
+            ares_set_servers_csv(channel_, "1.2.3.4 , 0102:0304:0506:0708:0910:1112:1314:1516, 2.3.4.5"));
+
+  // Same, with ports -- currently ignored
+  EXPECT_EQ(ARES_SUCCESS,
+            ares_set_servers_csv(channel_, "1.2.3.4:54,[0102:0304:0506:0708:0910:1112:1314:1516]:80,2.3.4.5:55"));
+  EXPECT_EQ(expected, GetNameServers(channel_));
+}
+
+TEST_F(DefaultChannelTest, TimeoutValue) {
+  struct timeval tinfo;
+  tinfo.tv_sec = 0;
+  tinfo.tv_usec = 0;
+  struct timeval tmax;
+  tmax.tv_sec = 0;
+  tmax.tv_usec = 10;
+  struct timeval* pt;
+
+  // No timers => get max back.
+  pt = ares_timeout(channel_, &tmax, &tinfo);
+  EXPECT_EQ(&tmax, pt);
+  EXPECT_EQ(0, pt->tv_sec);
+  EXPECT_EQ(10, pt->tv_usec);
+
+  pt = ares_timeout(channel_, nullptr, &tinfo);
+  EXPECT_EQ(nullptr, pt);
+
+  HostResult result;
+  ares_gethostbyname(channel_, "www.google.com.", AF_INET, HostCallback, &result);
+
+  // Now there's a timer running.
+  pt = ares_timeout(channel_, &tmax, &tinfo);
+  EXPECT_EQ(&tmax, pt);
+  EXPECT_EQ(0, pt->tv_sec);
+  EXPECT_EQ(10, pt->tv_usec);
+
+  tmax.tv_sec = 100;
+  pt = ares_timeout(channel_, &tmax, &tinfo);
+  EXPECT_EQ(&tinfo, pt);
+
+  pt = ares_timeout(channel_, nullptr, &tinfo);
+  EXPECT_EQ(&tinfo, pt);
+
+  Process();
+}
+
+TEST_F(LibraryTest, InetNtoP) {
+  struct in_addr addr;
+  addr.s_addr = htonl(0x01020304);
+  char buffer[256];
+  EXPECT_EQ(buffer, ares_inet_ntop(AF_INET, &addr, buffer, sizeof(buffer)));
+  EXPECT_EQ("1.2.3.4", std::string(buffer));
+}
+
+TEST_F(LibraryTest, Mkquery) {
+  byte* p;
+  int len;
+  ares_mkquery("example.com", ns_c_in, ns_t_a, 0x1234, 0, &p, &len);
+  std::vector<byte> data(p, p + len);
+  ares_free_string(p);
+
+  std::string actual = PacketToString(data);
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).add_question(new DNSQuestion("example.com", ns_t_a));
+  std::string expected = PacketToString(pkt.data());
+  EXPECT_EQ(expected, actual);
+}
+
+TEST_F(LibraryTest, CreateQuery) {
+  byte* p;
+  int len;
+  ares_create_query("exam\\@le.com", ns_c_in, ns_t_a, 0x1234, 0, &p, &len, 0);
+  std::vector<byte> data(p, p + len);
+  ares_free_string(p);
+
+  std::string actual = PacketToString(data);
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).add_question(new DNSQuestion("exam@le.com", ns_t_a));
+  std::string expected = PacketToString(pkt.data());
+  EXPECT_EQ(expected, actual);
+}
+
+TEST_F(LibraryTest, CreateEDNSQuery) {
+  byte* p;
+  int len;
+  ares_create_query("example.com", ns_c_in, ns_t_a, 0x1234, 0, &p, &len, 1280);
+  std::vector<byte> data(p, p + len);
+  ares_free_string(p);
+
+  std::string actual = PacketToString(data);
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).add_question(new DNSQuestion("example.com", ns_t_a))
+    .add_additional(new DNSOptRR(0, 1280));
+  std::string expected = PacketToString(pkt.data());
+  EXPECT_EQ(expected, actual);
+}
+
+TEST_F(LibraryTest, CreateRootQuery) {
+  byte* p;
+  int len;
+  ares_create_query(".", ns_c_in, ns_t_a, 0x1234, 0, &p, &len, 0);
+  std::vector<byte> data(p, p + len);
+  ares_free_string(p);
+
+  std::string actual = PacketToString(data);
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).add_question(new DNSQuestion("", ns_t_a));
+  std::string expected = PacketToString(pkt.data());
+  EXPECT_EQ(expected, actual);
+}
+
+TEST_F(LibraryTest, Version) {
+  // Assume linked to same version
+  EXPECT_EQ(std::string(ARES_VERSION_STR),
+            std::string(ares_version(nullptr)));
+  int version;
+  ares_version(&version);
+  EXPECT_EQ(ARES_VERSION, version);
+}
+
+TEST_F(LibraryTest, Strerror) {
+  EXPECT_EQ("Successful completion",
+            std::string(ares_strerror(ARES_SUCCESS)));
+  EXPECT_EQ("DNS query cancelled",
+            std::string(ares_strerror(ARES_ECANCELLED)));
+  EXPECT_EQ("unknown",
+            std::string(ares_strerror(99)));
+}
+
+TEST_F(LibraryTest, ExpandString) {
+  std::vector<byte> s1 = { 3, 'a', 'b', 'c'};
+  char* result;
+  long len;
+  EXPECT_EQ(ARES_SUCCESS,
+            ares_expand_string(s1.data(), s1.data(), s1.size(),
+                               (unsigned char**)&result, &len));
+  EXPECT_EQ("abc", std::string(result));
+  EXPECT_EQ(1 + 3, len);  // amount of data consumed includes 1 byte len
+  EXPECT_EQ(ARES_EBADSTR,
+            ares_expand_string(s1.data() + 1, s1.data(), s1.size(),
+                               (unsigned char**)&result, &len));
+  EXPECT_EQ(ARES_EBADSTR,
+            ares_expand_string(s1.data() + 4, s1.data(), s1.size(),
+                               (unsigned char**)&result, &len));
+}
+
+}  // namespace test
+}  // namespace ares
--- a/test/ares-test-mock.cc
+++ b/test/ares-test-mock.cc
@ -0,0 +1,139 @@
+#include "ares-test.h"
+#include "dns-proto.h"
+
+#include <sys/socket.h>
+
+#include <sstream>
+#include <vector>
+
+using testing::InvokeWithoutArgs;
+
+namespace ares {
+namespace test {
+
+TEST_F(MockChannelTest, Basic) {
+  std::vector<byte> reply = {
+    0x00, 0x00,  // qid
+    0x84, // response + query + AA + not-TC + not-RD
+    0x00, // not-RA + not-Z + not-AD + not-CD + rc=NoError
+    0x00, 0x01,  // 1 question
+    0x00, 0x01,  // 1 answer RRs
+    0x00, 0x00,  // 0 authority RRs
+    0x00, 0x00,  // 0 additional RRs
+    // Question
+    0x03, 'w', 'w', 'w',
+    0x06, 'g', 'o', 'o', 'g', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x01,  // type A
+    0x00, 0x01,  // class IN
+    // Answer
+    0x03, 'w', 'w', 'w',
+    0x06, 'g', 'o', 'o', 'g', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x01,  // type A
+    0x00, 0x01,  // class IN
+    0x00, 0x00, 0x01, 0x00,  // TTL
+    0x00, 0x04,  // rdata length
+    0x01, 0x02, 0x03, 0x04
+  };
+
+  EXPECT_CALL(server_, OnRequest("www.google.com", ns_t_a))
+    .WillOnce(SetReplyData(&server_, reply));
+
+  HostResult result;
+  ares_gethostbyname(channel_, "www.google.com.", AF_INET, HostCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+  std::stringstream ss;
+  ss << result.host_;
+  EXPECT_EQ("{'www.google.com' aliases=[] addrs=[1.2.3.4]}", ss.str());
+}
+
+TEST_F(MockChannelTest, SearchDomains) {
+  DNSPacket nofirst;
+  nofirst.set_response().set_aa().set_rcode(ns_r_nxdomain)
+    .add_question(new DNSQuestion("www.first.com", ns_t_a));
+  EXPECT_CALL(server_, OnRequest("www.first.com", ns_t_a))
+    .WillOnce(SetReply(&server_, &nofirst));
+  DNSPacket nosecond;
+  nosecond.set_response().set_aa().set_rcode(ns_r_nxdomain)
+    .add_question(new DNSQuestion("www.second.org", ns_t_a));
+  EXPECT_CALL(server_, OnRequest("www.second.org", ns_t_a))
+    .WillOnce(SetReply(&server_, &nosecond));
+  DNSPacket yesthird;
+  yesthird.set_response().set_aa()
+    .add_question(new DNSQuestion("www.third.gov", ns_t_a))
+    .add_answer(new DNSARR("www.third.gov", 0x0200, {2, 3, 4, 5}));
+  EXPECT_CALL(server_, OnRequest("www.third.gov", ns_t_a))
+    .WillOnce(SetReply(&server_, &yesthird));
+
+  HostResult result;
+  ares_gethostbyname(channel_, "www", AF_INET, HostCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+  std::stringstream ss;
+  ss << result.host_;
+  EXPECT_EQ("{'www.third.gov' aliases=[] addrs=[2.3.4.5]}", ss.str());
+}
+
+TEST_F(MockChannelTest, Resend) {
+  std::vector<byte> nothing;
+  DNSPacket reply;
+  reply.set_response().set_aa()
+    .add_question(new DNSQuestion("www.google.com", ns_t_a))
+    .add_answer(new DNSARR("www.google.com", 0x0100, {0x01, 0x02, 0x03, 0x04}));
+
+  EXPECT_CALL(server_, OnRequest("www.google.com", ns_t_a))
+    .WillOnce(SetReplyData(&server_, nothing))
+    .WillOnce(SetReplyData(&server_, nothing))
+    .WillOnce(SetReply(&server_, &reply));
+
+  HostResult result;
+  ares_gethostbyname(channel_, "www.google.com.", AF_INET, HostCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+  EXPECT_EQ(2, result.timeouts_);
+  std::stringstream ss;
+  ss << result.host_;
+  EXPECT_EQ("{'www.google.com' aliases=[] addrs=[1.2.3.4]}", ss.str());
+}
+
+TEST_F(MockChannelTest, CancelImmediate) {
+  HostResult result;
+  ares_gethostbyname(channel_, "www.google.com.", AF_INET, HostCallback, &result);
+  ares_cancel(channel_);
+  EXPECT_TRUE(result.done_);
+  EXPECT_EQ(ARES_ECANCELLED, result.status_);
+  EXPECT_EQ(0, result.timeouts_);
+}
+
+TEST_F(MockChannelTest, CancelLater) {
+  std::vector<byte> nothing;
+
+  // On second request, cancel the channel.
+  EXPECT_CALL(server_, OnRequest("www.google.com", ns_t_a))
+    .WillOnce(SetReplyData(&server_, nothing))
+    .WillOnce(CancelChannel(&server_, channel_));
+
+  HostResult result;
+  ares_gethostbyname(channel_, "www.google.com.", AF_INET, HostCallback, &result);
+  Process();
+  EXPECT_TRUE(result.done_);
+  EXPECT_EQ(ARES_ECANCELLED, result.status_);
+  EXPECT_EQ(0, result.timeouts_);
+}
+
+TEST_F(MockChannelTest, Destroy) {
+  HostResult result;
+  ares_gethostbyname(channel_, "www.google.com.", AF_INET, HostCallback, &result);
+  ares_destroy(channel_);
+  channel_ = nullptr;
+  EXPECT_TRUE(result.done_);
+  EXPECT_EQ(ARES_EDESTRUCTION, result.status_);
+  EXPECT_EQ(0, result.timeouts_);
+}
+
+}  // namespace test
+}  // namespace ares
--- a/test/ares-test-parse.cc
+++ b/test/ares-test-parse.cc
@ -0,0 +1,640 @@
+#include "ares-test.h"
+#include "dns-proto.h"
+
+#include <sstream>
+#include <vector>
+
+namespace ares {
+namespace test {
+
+TEST_F(LibraryTest, ParseAReplyOK) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("example.com", ns_t_a))
+    .add_answer(new DNSARR("example.com", 0x01020304, {0x02, 0x03, 0x04, 0x05}));
+  std::vector<byte> data = {
+    0x12, 0x34,  // qid
+    0x84, // response + query + AA + not-TC + not-RD
+    0x00, // not-RA + not-Z + not-AD + not-CD + rc=NoError
+    0x00, 0x01,  // num questions
+    0x00, 0x01,  // num answer RRs
+    0x00, 0x00,  // num authority RRs
+    0x00, 0x00,  // num additional RRs
+    // Question
+    0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x01,  // type A
+    0x00, 0x01,  // class IN
+    // Answer 1
+    0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x01,  // RR type
+    0x00, 0x01,  // class IN
+    0x01, 0x02, 0x03, 0x04, // TTL
+    0x00, 0x04,  // rdata length
+    0x02, 0x03, 0x04, 0x05,
+  };
+  EXPECT_EQ(data, pkt.data());
+  struct hostent *host = nullptr;
+  struct ares_addrttl info[5];
+  int count = 5;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_a_reply(data.data(), data.size(),
+                                             &host, info, &count));
+  EXPECT_EQ(1, count);
+  EXPECT_EQ(0x01020304, info[0].ttl);
+  unsigned long expected_addr = htonl(0x02030405);
+  EXPECT_EQ(expected_addr, info[0].ipaddr.s_addr);
+  ASSERT_NE(nullptr, host);
+  std::stringstream ss;
+  ss << HostEnt(host);
+  EXPECT_EQ("{'example.com' aliases=[] addrs=[2.3.4.5]}", ss.str());
+  ares_free_hostent(host);
+}
+
+TEST_F(LibraryTest, ParseAReplyErrors) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_answer(new DNSARR("example.com", 0x01020304, {0x02, 0x03, 0x04, 0x05}));
+  std::vector<byte> data = pkt.data();
+
+  struct hostent *host = nullptr;
+  struct ares_addrttl info[2];
+  int count = 2;
+  // No question
+  EXPECT_EQ(ARES_EBADRESP, ares_parse_a_reply(data.data(), data.size(),
+                                              &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+
+  // Question != answer
+  pkt.add_question(new DNSQuestion("Axample.com", ns_t_a));
+  data = pkt.data();
+  EXPECT_EQ(ARES_ENODATA, ares_parse_a_reply(data.data(), data.size(),
+                                              &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+  pkt.questions_.clear();
+  pkt.add_question(new DNSQuestion("example.com", ns_t_a));
+
+#ifdef DISABLED
+  // Not a response.
+  pkt.set_response(false);
+  data = pkt.data();
+  EXPECT_EQ(ARES_EBADRESP, ares_parse_a_reply(data.data(), data.size(),
+                                              &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+  pkt.set_response(true);
+
+  // Bad return code.
+  pkt.set_rcode(ns_r_formerr);
+  data = pkt.data();
+  EXPECT_EQ(ARES_ENODATA, ares_parse_a_reply(data.data(), data.size(),
+                                              &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+  pkt.set_rcode(ns_r_noerror);
+#endif
+
+  // 2 questions
+  pkt.add_question(new DNSQuestion("example.com", ns_t_a));
+  data = pkt.data();
+  EXPECT_EQ(ARES_EBADRESP, ares_parse_a_reply(data.data(), data.size(),
+                                              &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+
+  // Wrong sort of answer.
+  pkt.answers_.clear();
+  pkt.add_answer(new DNSMxRR("example.com", 0x01020304, 100, "mx1.example.com"));
+  data = pkt.data();
+  EXPECT_EQ(ARES_EBADRESP, ares_parse_a_reply(data.data(), data.size(),
+                                              &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+
+  // No answer
+  pkt.answers_.clear();
+  data = pkt.data();
+  EXPECT_EQ(ARES_EBADRESP, ares_parse_a_reply(data.data(), data.size(),
+                                              &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+  pkt.add_answer(new DNSARR("example.com", 0x01020304, {0x02, 0x03, 0x04, 0x05}));
+
+  // Truncated packets.
+  data = pkt.data();
+  for (size_t len = 1; len < data.size(); len++) {
+    EXPECT_EQ(ARES_EBADRESP, ares_parse_a_reply(data.data(), len,
+                                                &host, info, &count));
+    EXPECT_EQ(nullptr, host);
+  }
+}
+
+TEST_F(LibraryTest, ParseAReplyAllocFail) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("Axample.com", ns_t_a))
+    .add_answer(new DNSARR("example.com", 0x01020304, {0x02, 0x03, 0x04, 0x05}));
+  std::vector<byte> data = pkt.data();
+
+  struct hostent *host = nullptr;
+  struct ares_addrttl info[2];
+  int count = 2;
+  SetAllocSizeFail(1 * sizeof(struct in_addr));
+  EXPECT_EQ(ARES_ENOMEM, ares_parse_a_reply(data.data(), data.size(),
+                                            &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+
+  SetAllocSizeFail(2 * sizeof(char *));
+  EXPECT_EQ(ARES_ENOMEM, ares_parse_a_reply(data.data(), data.size(),
+                                            &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+
+}
+
+TEST_F(LibraryTest, ParseAaaaReplyOK) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("example.com", ns_t_aaaa))
+    .add_answer(new DNSAaaaRR("example.com", 0x01020304,
+                              {0x01, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02, 0x02,
+                               0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04}));
+  std::vector<byte> data = pkt.data();
+  struct hostent *host = nullptr;
+  struct ares_addr6ttl info[5];
+  int count = 5;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_aaaa_reply(data.data(), data.size(),
+                                                &host, info, &count));
+  EXPECT_EQ(1, count);
+  EXPECT_EQ(0x01020304, info[0].ttl);
+  EXPECT_EQ(0x01, info[0].ip6addr._S6_un._S6_u8[0]);
+  EXPECT_EQ(0x02, info[0].ip6addr._S6_un._S6_u8[4]);
+  ASSERT_NE(nullptr, host);
+  std::stringstream ss;
+  ss << HostEnt(host);
+  EXPECT_EQ("{'example.com' aliases=[] addrs=[0101:0101:0202:0202:0303:0303:0404:0404]}", ss.str());
+  ares_free_hostent(host);
+}
+
+TEST_F(LibraryTest, ParseAaaaReplyErrors) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_answer(new DNSAaaaRR("example.com", 0x01020304,
+                              {0x01, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02, 0x02,
+                               0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04}));
+  std::vector<byte> data = pkt.data();
+
+  struct hostent *host = nullptr;
+  struct ares_addr6ttl info[2];
+  int count = 2;
+  // No question
+  EXPECT_EQ(ARES_EBADRESP, ares_parse_aaaa_reply(data.data(), data.size(),
+                                                 &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+
+  // Question != answer
+  pkt.add_question(new DNSQuestion("Axample.com", ns_t_aaaa));
+  data = pkt.data();
+  EXPECT_EQ(ARES_ENODATA, ares_parse_aaaa_reply(data.data(), data.size(),
+                                                &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+  pkt.questions_.clear();
+  pkt.add_question(new DNSQuestion("example.com", ns_t_aaaa));
+
+  // 2 questions
+  pkt.add_question(new DNSQuestion("example.com", ns_t_aaaa));
+  data = pkt.data();
+  EXPECT_EQ(ARES_EBADRESP, ares_parse_aaaa_reply(data.data(), data.size(),
+                                                 &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+
+  // Wrong sort of answer.
+  pkt.answers_.clear();
+  pkt.add_answer(new DNSMxRR("example.com", 0x01020304, 100, "mx1.example.com"));
+  data = pkt.data();
+  EXPECT_EQ(ARES_EBADRESP, ares_parse_aaaa_reply(data.data(), data.size(),
+                                                  &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+
+  // No answer
+  pkt.answers_.clear();
+  data = pkt.data();
+  EXPECT_EQ(ARES_EBADRESP, ares_parse_aaaa_reply(data.data(), data.size(),
+                                                 &host, info, &count));
+  EXPECT_EQ(nullptr, host);
+  pkt.add_answer(new DNSAaaaRR("example.com", 0x01020304,
+                              {0x01, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02, 0x02,
+                               0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04}));
+
+  // Truncated packets.
+  data = pkt.data();
+  for (size_t len = 1; len < data.size(); len++) {
+    EXPECT_EQ(ARES_EBADRESP, ares_parse_aaaa_reply(data.data(), len,
+                                                   &host, info, &count));
+    EXPECT_EQ(nullptr, host);
+  }
+}
+
+TEST_F(LibraryTest, ParsePtrReplyOK) {
+  byte addrv4[4] = {0x10, 0x20, 0x30, 0x40};
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("64.48.32.16.in-addr.arpa", ns_t_ptr))
+    .add_answer(new DNSPtrRR("64.48.32.16.in-addr.arpa", 0x01020304, "other.com"));
+  std::vector<byte> data = pkt.data();
+
+  struct hostent *host = nullptr;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_ptr_reply(data.data(), data.size(),
+                                               addrv4, sizeof(addrv4), AF_INET, &host));
+  ASSERT_NE(nullptr, host);
+  std::stringstream ss;
+  ss << HostEnt(host);
+  EXPECT_EQ("{'other.com' aliases=[other.com] addrs=[16.32.48.64]}", ss.str());
+  ares_free_hostent(host);
+}
+
+TEST_F(LibraryTest, ParseNsReplyOK) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("example.com", ns_t_ns))
+    .add_answer(new DNSNsRR("example.com", 0x01020304, "ns.example.com"));
+  std::vector<byte> data = pkt.data();
+
+  struct hostent *host = nullptr;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_ns_reply(data.data(), data.size(), &host));
+  ASSERT_NE(nullptr, host);
+  std::stringstream ss;
+  ss << HostEnt(host);
+  EXPECT_EQ("{'example.com' aliases=[ns.example.com] addrs=[]}", ss.str());
+  ares_free_hostent(host);
+}
+
+TEST_F(LibraryTest, ParseSrvReplyOK) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("example.com", ns_t_srv))
+    .add_answer(new DNSSrvRR("example.com", 0x01020304, 10, 20, 30, "srv.example.com"))
+    .add_answer(new DNSSrvRR("example.com", 0x01020304, 11, 21, 31, "srv2.example.com"));
+  std::vector<byte> data = pkt.data();
+
+  struct ares_srv_reply* srv = nullptr;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_srv_reply(data.data(), data.size(), &srv));
+  ASSERT_NE(nullptr, srv);
+
+  EXPECT_EQ("srv.example.com", std::string(srv->host));
+  EXPECT_EQ(10, srv->priority);
+  EXPECT_EQ(20, srv->weight);
+  EXPECT_EQ(30, srv->port);
+
+  struct ares_srv_reply* srv2 = srv->next;
+  ASSERT_NE(nullptr, srv2);
+  EXPECT_EQ("srv2.example.com", std::string(srv2->host));
+  EXPECT_EQ(11, srv2->priority);
+  EXPECT_EQ(21, srv2->weight);
+  EXPECT_EQ(31, srv2->port);
+  EXPECT_EQ(nullptr, srv2->next);
+
+  ares_free_data(srv);
+}
+
+TEST_F(LibraryTest, ParseMxReplyOK) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("example.com", ns_t_mx))
+    .add_answer(new DNSMxRR("example.com", 0x01020304, 100, "mx1.example.com"))
+    .add_answer(new DNSMxRR("example.com", 0x01020304, 200, "mx2.example.com"));
+  std::vector<byte> data = pkt.data();
+
+  struct ares_mx_reply* mx = nullptr;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_mx_reply(data.data(), data.size(), &mx));
+  ASSERT_NE(nullptr, mx);
+  EXPECT_EQ("mx1.example.com", std::string(mx->host));
+  EXPECT_EQ(100, mx->priority);
+
+  struct ares_mx_reply* mx2 = mx->next;
+  ASSERT_NE(nullptr, mx2);
+  EXPECT_EQ("mx2.example.com", std::string(mx2->host));
+  EXPECT_EQ(200, mx2->priority);
+  EXPECT_EQ(nullptr, mx2->next);
+
+  ares_free_data(mx);
+}
+
+TEST_F(LibraryTest, ParseTxtReplyOK) {
+  DNSPacket pkt;
+  std::string expected1 = "txt1.example.com";
+  std::string expected2a = "txt2a";
+  std::string expected2b("ABC\0ABC", 7);
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("example.com", ns_t_mx))
+    .add_answer(new DNSTxtRR("example.com", 0x01020304, {expected1}))
+    .add_answer(new DNSTxtRR("example.com", 0x01020304, {expected2a, expected2b}));
+  std::vector<byte> data = pkt.data();
+
+  struct ares_txt_reply* txt = nullptr;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_txt_reply(data.data(), data.size(), &txt));
+  ASSERT_NE(nullptr, txt);
+  EXPECT_EQ(std::vector<byte>(expected1.data(), expected1.data() + expected1.size()),
+            std::vector<byte>(txt->txt, txt->txt + txt->length));
+
+  struct ares_txt_reply* txt2 = txt->next;
+  ASSERT_NE(nullptr, txt2);
+  EXPECT_EQ(std::vector<byte>(expected2a.data(), expected2a.data() + expected2a.size()),
+            std::vector<byte>(txt2->txt, txt2->txt + txt2->length));
+
+  struct ares_txt_reply* txt3 = txt2->next;
+  ASSERT_NE(nullptr, txt3);
+  EXPECT_EQ(std::vector<byte>(expected2b.data(), expected2b.data() + expected2b.size()),
+            std::vector<byte>(txt3->txt, txt3->txt + txt3->length));
+  EXPECT_EQ(nullptr, txt3->next);
+
+  ares_free_data(txt);
+}
+
+TEST_F(LibraryTest, ParseTxtReplyErrors) {
+  DNSPacket pkt;
+  std::string expected1 = "txt1.example.com";
+  std::string expected2a = "txt2a";
+  std::string expected2b = "txt2b";
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("example.com", ns_t_mx))
+    .add_answer(new DNSTxtRR("example.com", 0x01020304, {expected1}))
+    .add_answer(new DNSTxtRR("example.com", 0x01020304, {expected1}))
+    .add_answer(new DNSTxtRR("example.com", 0x01020304, {expected2a, expected2b}));
+  std::vector<byte> data = pkt.data();
+  struct ares_txt_reply* txt = nullptr;
+
+  // Truncated packets.
+  for (size_t len = 1; len < data.size(); len++) {
+    txt = nullptr;
+    EXPECT_NE(ARES_SUCCESS, ares_parse_txt_reply(data.data(), len, &txt));
+    EXPECT_EQ(nullptr, txt);
+  }
+
+  // No question
+  pkt.questions_.clear();
+  data = pkt.data();
+  txt = nullptr;
+  EXPECT_EQ(ARES_EBADRESP, ares_parse_txt_reply(data.data(), data.size(), &txt));
+  EXPECT_EQ(nullptr, txt);
+  pkt.add_question(new DNSQuestion("example.com", ns_t_mx));
+
+  // No answer
+  pkt.answers_.clear();
+  data = pkt.data();
+  txt = nullptr;
+  EXPECT_EQ(ARES_ENODATA, ares_parse_txt_reply(data.data(), data.size(), &txt));
+  EXPECT_EQ(nullptr, txt);
+  pkt.add_answer(new DNSTxtRR("example.com", 0x01020304, {expected1}));
+}
+
+TEST_F(LibraryTest, ParseSoaReplyOK) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("example.com", ns_t_soa))
+    .add_answer(new DNSSoaRR("example.com", 0x01020304,
+                             "soa1.example.com", "fred.example.com",
+                             1, 2, 3, 4, 5));
+  std::vector<byte> data = pkt.data();
+
+  struct ares_soa_reply* soa = nullptr;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_soa_reply(data.data(), data.size(), &soa));
+  ASSERT_NE(nullptr, soa);
+  EXPECT_EQ("soa1.example.com", std::string(soa->nsname));
+  EXPECT_EQ("fred.example.com", std::string(soa->hostmaster));
+  EXPECT_EQ(1, soa->serial);
+  EXPECT_EQ(2, soa->refresh);
+  EXPECT_EQ(3, soa->retry);
+  EXPECT_EQ(4, soa->expire);
+  EXPECT_EQ(5, soa->minttl);
+  ares_free_data(soa);
+}
+
+TEST_F(LibraryTest, ParseNaptrReplyOK) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("example.com", ns_t_soa))
+    .add_answer(new DNSNaptrRR("example.com", 0x01020304,
+                               10, 20, "SP", "service", "regexp", "replace"));
+  std::vector<byte> data = pkt.data();
+
+  struct ares_naptr_reply* naptr = nullptr;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_naptr_reply(data.data(), data.size(), &naptr));
+  ASSERT_NE(nullptr, naptr);
+  EXPECT_EQ("SP", std::string((char*)naptr->flags));
+  EXPECT_EQ("service", std::string((char*)naptr->service));
+  EXPECT_EQ("regexp", std::string((char*)naptr->regexp));
+  EXPECT_EQ("replace", std::string((char*)naptr->replacement));
+  EXPECT_EQ(10, naptr->order);
+  EXPECT_EQ(20, naptr->preference);
+  EXPECT_EQ(nullptr, naptr->next);
+
+  ares_free_data(naptr);
+}
+
+TEST_F(LibraryTest, ParseRootName) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion(".", ns_t_a))
+    .add_answer(new DNSARR(".", 0x01020304, {0x02, 0x03, 0x04, 0x05}));
+  std::vector<byte> data = pkt.data();
+
+  struct hostent *host = nullptr;
+  struct ares_addrttl info[2];
+  int count = 2;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_a_reply(data.data(), data.size(),
+                                             &host, info, &count));
+  EXPECT_EQ(1, count);
+  std::stringstream ss;
+  ss << HostEnt(host);
+  EXPECT_EQ("{'' aliases=[] addrs=[2.3.4.5]}", ss.str());
+  ares_free_hostent(host);
+}
+
+TEST_F(LibraryTest, ParseIndirectRootName) {
+  std::vector<byte> data = {
+    0x12, 0x34,  // qid
+    0x84, // response + query + AA + not-TC + not-RD
+    0x00, // not-RA + not-Z + not-AD + not-CD + rc=NoError
+    0x00, 0x01,  // num questions
+    0x00, 0x01,  // num answer RRs
+    0x00, 0x00,  // num authority RRs
+    0x00, 0x00,  // num additional RRs
+    // Question
+    0xC0, 0x04,  // weird: pointer to a random zero earlier in the message
+    0x00, 0x01,  // type A
+    0x00, 0x01,  // class IN
+    // Answer 1
+    0xC0, 0x04,
+    0x00, 0x01,  // RR type
+    0x00, 0x01,  // class IN
+    0x01, 0x02, 0x03, 0x04, // TTL
+    0x00, 0x04,  // rdata length
+    0x02, 0x03, 0x04, 0x05,
+  };
+
+  struct hostent *host = nullptr;
+  struct ares_addrttl info[2];
+  int count = 2;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_a_reply(data.data(), data.size(),
+                                             &host, info, &count));
+  EXPECT_EQ(1, count);
+  std::stringstream ss;
+  ss << HostEnt(host);
+  EXPECT_EQ("{'' aliases=[] addrs=[2.3.4.5]}", ss.str());
+  ares_free_hostent(host);
+}
+
+TEST_F(LibraryTest, ParseEscapedName) {
+  std::vector<byte> data = {
+    0x12, 0x34,  // qid
+    0x84, // response + query + AA + not-TC + not-RD
+    0x00, // not-RA + not-Z + not-AD + not-CD + rc=NoError
+    0x00, 0x01,  // num questions
+    0x00, 0x01,  // num answer RRs
+    0x00, 0x00,  // num authority RRs
+    0x00, 0x00,  // num additional RRs
+    // Question
+    0x05, 'a', '\\', 'b', '.', 'c',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x01,  // type A
+    0x00, 0x01,  // class IN
+    // Answer 1
+    0x05, 'a', '\\', 'b', '.', 'c',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x01,  // RR type
+    0x00, 0x01,  // class IN
+    0x01, 0x02, 0x03, 0x04, // TTL
+    0x00, 0x04,  // rdata length
+    0x02, 0x03, 0x04, 0x05,
+  };
+  struct hostent *host = nullptr;
+  struct ares_addrttl info[2];
+  int count = 2;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_a_reply(data.data(), data.size(),
+                                             &host, info, &count));
+  EXPECT_EQ(1, count);
+  HostEnt hent(host);
+  std::stringstream ss;
+  ss << hent;
+  // The printable name is expanded with escapes.
+  EXPECT_EQ(11, hent.name_.size());
+  EXPECT_EQ('a', hent.name_[0]);
+  EXPECT_EQ('\\', hent.name_[1]);
+  EXPECT_EQ('\\', hent.name_[2]);
+  EXPECT_EQ('b', hent.name_[3]);
+  EXPECT_EQ('\\', hent.name_[4]);
+  EXPECT_EQ('.', hent.name_[5]);
+  EXPECT_EQ('c', hent.name_[6]);
+  ares_free_hostent(host);
+}
+
+TEST_F(LibraryTest, ParsePartialCompressedName) {
+  std::vector<byte> data = {
+    0x12, 0x34,  // qid
+    0x84, // response + query + AA + not-TC + not-RD
+    0x00, // not-RA + not-Z + not-AD + not-CD + rc=NoError
+    0x00, 0x01,  // num questions
+    0x00, 0x01,  // num answer RRs
+    0x00, 0x00,  // num authority RRs
+    0x00, 0x00,  // num additional RRs
+    // Question
+    0x03, 'w', 'w', 'w',
+    0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x01,  // type A
+    0x00, 0x01,  // class IN
+    // Answer 1
+    0x03, 'w', 'w', 'w',
+    0xc0, 0x10,  // offset 16
+    0x00, 0x01,  // RR type
+    0x00, 0x01,  // class IN
+    0x01, 0x02, 0x03, 0x04, // TTL
+    0x00, 0x04,  // rdata length
+    0x02, 0x03, 0x04, 0x05,
+  };
+  struct hostent *host = nullptr;
+  struct ares_addrttl info[2];
+  int count = 2;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_a_reply(data.data(), data.size(),
+                                             &host, info, &count));
+  ASSERT_NE(nullptr, host);
+  std::stringstream ss;
+  ss << HostEnt(host);
+  EXPECT_EQ("{'www.example.com' aliases=[] addrs=[2.3.4.5]}", ss.str());
+  ares_free_hostent(host);
+}
+
+TEST_F(LibraryTest, ParseFullyCompressedName) {
+  std::vector<byte> data = {
+    0x12, 0x34,  // qid
+    0x84, // response + query + AA + not-TC + not-RD
+    0x00, // not-RA + not-Z + not-AD + not-CD + rc=NoError
+    0x00, 0x01,  // num questions
+    0x00, 0x01,  // num answer RRs
+    0x00, 0x00,  // num authority RRs
+    0x00, 0x00,  // num additional RRs
+    // Question
+    0x03, 'w', 'w', 'w',
+    0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x01,  // type A
+    0x00, 0x01,  // class IN
+    // Answer 1
+    0xc0, 0x0c,  // offset 12
+    0x00, 0x01,  // RR type
+    0x00, 0x01,  // class IN
+    0x01, 0x02, 0x03, 0x04, // TTL
+    0x00, 0x04,  // rdata length
+    0x02, 0x03, 0x04, 0x05,
+  };
+  struct hostent *host = nullptr;
+  struct ares_addrttl info[2];
+  int count = 2;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_a_reply(data.data(), data.size(),
+                                             &host, info, &count));
+  ASSERT_NE(nullptr, host);
+  std::stringstream ss;
+  ss << HostEnt(host);
+  EXPECT_EQ("{'www.example.com' aliases=[] addrs=[2.3.4.5]}", ss.str());
+  ares_free_hostent(host);
+}
+
+TEST_F(LibraryTest, ParseFullyCompressedName2) {
+  std::vector<byte> data = {
+    0x12, 0x34,  // qid
+    0x84, // response + query + AA + not-TC + not-RD
+    0x00, // not-RA + not-Z + not-AD + not-CD + rc=NoError
+    0x00, 0x01,  // num questions
+    0x00, 0x01,  // num answer RRs
+    0x00, 0x00,  // num authority RRs
+    0x00, 0x00,  // num additional RRs
+    // Question
+    0xC0, 0x12,  // pointer to later in message
+    0x00, 0x01,  // type A
+    0x00, 0x01,  // class IN
+    // Answer 1
+    0x03, 'w', 'w', 'w',
+    0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x01,  // RR type
+    0x00, 0x01,  // class IN
+    0x01, 0x02, 0x03, 0x04, // TTL
+    0x00, 0x04,  // rdata length
+    0x02, 0x03, 0x04, 0x05,
+  };
+  struct hostent *host = nullptr;
+  struct ares_addrttl info[2];
+  int count = 2;
+  EXPECT_EQ(ARES_SUCCESS, ares_parse_a_reply(data.data(), data.size(),
+                                             &host, info, &count));
+  ASSERT_NE(nullptr, host);
+  std::stringstream ss;
+  ss << HostEnt(host);
+  EXPECT_EQ("{'www.example.com' aliases=[] addrs=[2.3.4.5]}", ss.str());
+  ares_free_hostent(host);
+}
+
+}  // namespace test
+}  // namespace ares
--- a/test/ares-test.cc
+++ b/test/ares-test.cc
@ -0,0 +1,385 @@
+#include "ares-test.h"
+#include "dns-proto.h"
+
+// Include ares internal files for DNS protocol details
+#include "nameser.h"
+#include "ares_dns.h"
+
+#include <netdb.h>
+
+#include <functional>
+#include <sstream>
+
+namespace ares {
+namespace test {
+
+namespace {
+
+void ProcessWork(ares_channel channel,
+                 int extrafd, std::function<void(int)> process_extra) {
+  int nfds, count;
+  fd_set readers, writers;
+  struct timeval tv;
+  struct timeval* tvp;
+  while (true) {
+    // Retrieve the set of file descriptors that the library wants us to monitor.
+    FD_ZERO(&readers);
+    FD_ZERO(&writers);
+    nfds = ares_fds(channel, &readers, &writers);
+
+    // Add in the extra FD if present
+    if (extrafd >= 0)
+      FD_SET(extrafd, &readers);
+
+    if (nfds == 0)  // no work left to do
+      return;
+
+    // Also retrieve the timeout value that the library wants us to use.
+    tvp = ares_timeout(channel, nullptr, &tv);
+    EXPECT_EQ(tvp, &tv);
+
+    // Wait for activity or timeout.
+    count = select(nfds, &readers, &writers, nullptr, tvp);
+    if (count < 0) {
+      fprintf(stderr, "select() failed, errno %d\n", errno);
+      return;
+    }
+
+    // Let the library process any activity.
+    ares_process(channel, &readers, &writers);
+    // Let the provided callback process any activity on the extra FD.
+    if (extrafd > 0 && FD_ISSET(extrafd, &readers))
+      process_extra(extrafd);
+  }
+}
+
+}  // namespace
+
+bool verbose = false;
+
+unsigned long LibraryTest::fails_ = 0;
+std::map<size_t, int> LibraryTest::size_fails_;
+
+// static
+void LibraryTest::SetAllocFail(int nth) {
+  assert(nth > 0);
+  fails_ |= (1 << (nth - 1));
+}
+
+// static
+void LibraryTest::SetAllocSizeFail(size_t size) {
+  size_fails_[size]++;
+}
+
+// static
+void LibraryTest::ClearFails() {
+  fails_ = 0;
+  size_fails_.clear();
+}
+
+
+// static
+bool LibraryTest::ShouldAllocFail(size_t size) {
+  bool fail = (fails_ & 0x01);
+  fails_ >>= 1;
+  if (size_fails_[size] > 0) {
+    size_fails_[size]--;
+    fail = true;
+  }
+  return fail;
+}
+
+// static
+void* LibraryTest::amalloc(size_t size) {
+  if (ShouldAllocFail(size)) {
+    if (verbose) std::cerr << "Failing malloc(" << size << ") request" << std::endl;
+    return nullptr;
+  } else {
+    return malloc(size);
+  }
+}
+
+// static
+void* LibraryTest::arealloc(void *ptr, size_t size) {
+  if (ShouldAllocFail(size)) {
+    if (verbose) std::cerr << "Failing realloc(" << ptr << ", " << size << ") request" << std::endl;
+    return nullptr;
+  } else {
+    return realloc(ptr, size);
+  }
+}
+
+// static
+void LibraryTest::afree(void *ptr) {
+  free(ptr);
+}
+
+void DefaultChannelTest::Process() {
+  ProcessWork(channel_, -1, nullptr);
+}
+
+MockServer::MockServer(int port) : port_(port) {
+  // Create a UDP socket to receive data on.
+  sockfd_ = socket(AF_INET, SOCK_DGRAM, 0);
+  EXPECT_NE(-1, sockfd_);
+
+  // Bind it to the given port.
+  struct sockaddr_in addr;
+  memset(&addr, 0, sizeof(addr));
+  addr.sin_family = AF_INET;
+  addr.sin_addr.s_addr = htonl(INADDR_ANY);
+  addr.sin_port = htons(port_);
+  int rc = bind(sockfd_, (struct sockaddr*)&addr, sizeof(addr));
+  EXPECT_EQ(0, rc) << "Failed to bind to port " << port_;
+}
+
+MockServer::~MockServer() {
+  close(sockfd_);
+  sockfd_ = -1;
+}
+
+void MockServer::Process(int fd) {
+  if (fd != sockfd_) return;
+  struct sockaddr_storage addr;
+  socklen_t addrlen = sizeof(addr);
+  byte buffer[2048];
+  int len = recvfrom(fd, buffer, sizeof(buffer), 0,
+                     (struct sockaddr *)&addr, &addrlen);
+
+  // Assume the packet is a well-formed DNS request and extract the request
+  // details.
+  if (len < NS_HFIXEDSZ) {
+    std::cerr << "Packet too short (" << len << ")" << std::endl;
+    return;
+  }
+  int qid = DNS_HEADER_QID(buffer);
+  if (DNS_HEADER_QR(buffer) != 0) {
+    std::cerr << "Not a request" << std::endl;
+    return;
+  }
+  if (DNS_HEADER_OPCODE(buffer) != ns_o_query) {
+    std::cerr << "Not a query (opcode " << DNS_HEADER_OPCODE(buffer)
+              << ")" << std::endl;
+    return;
+  }
+  if (DNS_HEADER_QDCOUNT(buffer) != 1) {
+    std::cerr << "Unexpected question count (" << DNS_HEADER_QDCOUNT(buffer)
+              << ")" << std::endl;
+    return;
+  }
+  byte* question = buffer + 12;
+  int qlen = len - 12;
+
+  char *name = nullptr;
+  long enclen;
+  ares_expand_name(question, buffer, len, &name, &enclen);
+  qlen -= enclen;
+  question += enclen;
+  std::string namestr(name);
+  free(name);
+
+  if (qlen < 4) {
+    std::cerr << "Unexpected question size (" << qlen
+              << " bytes after name)" << std::endl;
+    return;
+  }
+  if (DNS_QUESTION_CLASS(question) != ns_c_in) {
+    std::cerr << "Unexpected question class (" << DNS_QUESTION_CLASS(question)
+              << ")" << std::endl;
+    return;
+  }
+  int rrtype = DNS_QUESTION_TYPE(question);
+
+  if (verbose) std::cerr << "ProcessRequest(" << qid << ", '" << namestr
+                         << "', " << RRTypeToString(rrtype) << ")" << std::endl;
+  ProcessRequest(&addr, addrlen, qid, namestr, rrtype);
+}
+
+void MockServer::ProcessRequest(struct sockaddr_storage* addr, int addrlen,
+                                int qid, const std::string& name, int rrtype) {
+  // Before processing, let gMock know the request is happening.
+  OnRequest(name, rrtype);
+
+  // Send the current pending reply.  First overwrite the qid with the value
+  // from the argument.
+  if (reply_.size() <  2) {
+    if (verbose) std::cerr << "Skipping reply as not-present/too-short" << std::endl;
+    return;
+  }
+  reply_[0] = (byte)((qid >> 8) & 0xff);
+  reply_[1] = (byte)(qid & 0xff);
+  if (verbose) std::cerr << "sending reply " << PacketToString(reply_) << std::endl;
+  int rc = sendto(sockfd_, reply_.data(), reply_.size(), 0,
+                  (struct sockaddr *)addr, addrlen);
+  if (rc < static_cast<int>(reply_.size())) {
+    std::cerr << "Failed to send full reply, rc=" << rc << std::endl;
+  }
+}
+
+MockChannelOptsTest::MockChannelOptsTest(struct ares_options* givenopts,
+                                         int optmask)
+    : server_(5300), channel_(nullptr) {
+  // Set up channel options.
+  struct ares_options opts;
+  if (givenopts) {
+    memcpy(&opts, givenopts, sizeof(opts));
+  } else {
+    EXPECT_EQ(0, optmask);
+    memset(&opts, 0, sizeof(opts));
+  }
+
+  // Force communication with the mock server.
+  opts.udp_port = server_.port();
+  optmask |= ARES_OPT_UDP_PORT;
+  opts.tcp_port = server_.port();
+  optmask |= ARES_OPT_TCP_PORT;
+  opts.nservers = 1;
+  struct in_addr server_addr;
+  memset(&server_addr, 0, sizeof(server_addr));
+  server_addr.s_addr = htonl(0x7F000001);
+  opts.servers = &server_addr;
+  optmask |= ARES_OPT_SERVERS;
+
+  // If not already overridden, set short timeouts.
+  if (!(optmask & (ARES_OPT_TIMEOUTMS|ARES_OPT_TIMEOUT))) {
+    opts.timeout = 100;
+    optmask |= ARES_OPT_TIMEOUTMS;
+  }
+  // If not already overridden, set 3 retries.
+  if (!(optmask & ARES_OPT_TRIES)) {
+    opts.tries = 3;
+    optmask |= ARES_OPT_TRIES;
+  }
+  // If not already overridden, set search domains.
+  const char *domains[3] = {"first.com", "second.org", "third.gov"};
+  if (!(optmask & ARES_OPT_DOMAINS)) {
+    opts.ndomains = 3;
+    opts.domains = (char**)domains;
+    optmask |= ARES_OPT_DOMAINS;
+  }
+
+  EXPECT_EQ(ARES_SUCCESS, ares_init_options(&channel_, &opts, optmask));
+  EXPECT_NE(nullptr, channel_);
+}
+
+MockChannelOptsTest::~MockChannelOptsTest() {
+  if (channel_) {
+    ares_destroy(channel_);
+  }
+  channel_ = nullptr;
+}
+
+void MockChannelOptsTest::Process() {
+  using namespace std::placeholders;
+  ProcessWork(channel_, server_.sockfd(),
+              std::bind(&MockServer::Process, &server_, _1));
+}
+
+std::ostream& operator<<(std::ostream& os, const HostResult& result) {
+  os << '{';
+  if (result.done_) {
+    os << StatusToString(result.status_) << " " << result.host_;
+  } else {
+    os << "(incomplete)";
+  }
+  os << '}';
+  return os;
+}
+
+HostEnt::HostEnt(const struct hostent *hostent) {
+  if (!hostent) return;
+  if (hostent->h_name) name_ = hostent->h_name;
+  if (hostent->h_aliases) {
+    char** palias = hostent->h_aliases;
+    while (*palias != nullptr) {
+      aliases_.push_back(*palias);
+      palias++;
+    }
+  }
+  addrtype_ = hostent->h_addrtype;
+  if (hostent->h_addr_list) {
+    char** paddr = hostent->h_addr_list;
+    while (*paddr != nullptr) {
+      std::string addr = AddressToString(*paddr, hostent->h_length);
+      addrs_.push_back(addr);
+      paddr++;
+    }
+  }
+}
+
+std::ostream& operator<<(std::ostream& os, const HostEnt& host) {
+  os << '{';
+  os << "'" << host.name_ << "' "
+     << "aliases=[";
+  for (size_t ii = 0; ii < host.aliases_.size(); ii++) {
+    if (ii > 0) os << ", ";
+    os << host.aliases_[ii];
+  }
+  os << "] ";
+  os << "addrs=[";
+  for (size_t ii = 0; ii < host.addrs_.size(); ii++) {
+    if (ii > 0) os << ", ";
+    os << host.addrs_[ii];
+  }
+  os << "]";
+  os << '}';
+  return os;
+}
+void HostCallback(void *data, int status, int timeouts,
+                  struct hostent *hostent) {
+  EXPECT_NE(nullptr, data);
+  HostResult* result = reinterpret_cast<HostResult*>(data);
+  result->done_ = true;
+  result->status_ = status;
+  result->timeouts_ = timeouts;
+  result->host_ = HostEnt(hostent);
+  if (verbose) std::cerr << "HostCallback(" << *result << ")" << std::endl;
+}
+
+std::ostream& operator<<(std::ostream& os, const SearchResult& result) {
+  os << '{';
+  if (result.done_) {
+    os << StatusToString(result.status_) << " " << PacketToString(result.data_);
+  } else {
+    os << "(incomplete)";
+  }
+  os << '}';
+  return os;
+}
+
+void SearchCallback(void *data, int status, int timeouts,
+                    unsigned char *abuf, int alen) {
+  EXPECT_NE(nullptr, data);
+  SearchResult* result = reinterpret_cast<SearchResult*>(data);
+  result->done_ = true;
+  result->status_ = status;
+  result->timeouts_ = timeouts;
+  result->data_.assign(abuf, abuf + alen);
+  if (verbose) std::cerr << "SearchCallback(" << *result << ")" << std::endl;
+}
+
+std::ostream& operator<<(std::ostream& os, const NameInfoResult& result) {
+  os << '{';
+  if (result.done_) {
+    os << StatusToString(result.status_) << " " << result.node_ << " " << result.service_;
+  } else {
+    os << "(incomplete)";
+  }
+  os << '}';
+  return os;
+}
+
+void NameInfoCallback(void *data, int status, int timeouts,
+                      char *node, char *service) {
+  EXPECT_NE(nullptr, data);
+  NameInfoResult* result = reinterpret_cast<NameInfoResult*>(data);
+  result->done_ = true;
+  result->status_ = status;
+  result->timeouts_ = timeouts;
+  result->node_ = std::string(node ? node : "");
+  result->service_ = std::string(service ? service : "");
+  if (verbose) std::cerr << "NameInfoCallback(" << *result << ")" << std::endl;
+}
+
+}  // namespace test
+}  // namespace ares
--- a/test/ares-test.h
+++ b/test/ares-test.h
@ -0,0 +1,197 @@
+// -*- mode: c++ -*-
+#ifndef ARES_TEST_H
+#define ARES_TEST_H
+
+#include "ares.h"
+
+#include "dns-proto.h"
+
+// Include ares internal file for DNS protocol constants
+#include "nameser.h"
+
+#include "gtest/gtest.h"
+#include "gmock/gmock.h"
+
+#include <map>
+
+namespace ares {
+
+typedef unsigned char byte;
+
+namespace test {
+
+extern bool verbose;
+
+// Test fixture that ensures library initialization, and allows
+// memory allocations to be failed.
+class LibraryTest : public ::testing::Test {
+ public:
+  LibraryTest() {
+    EXPECT_EQ(ARES_SUCCESS,
+              ares_library_init_mem(ARES_LIB_INIT_ALL,
+                                    &LibraryTest::amalloc,
+                                    &LibraryTest::afree,
+                                    &LibraryTest::arealloc));
+  }
+  ~LibraryTest() {
+    ares_library_cleanup();
+    ClearFails();
+  }
+  // Set the n-th malloc call (of any size) from the library to fail.
+  // (nth == 1 means the next call)
+  static void SetAllocFail(int nth);
+  // Set the next malloc call for the given size to fail.
+  static void SetAllocSizeFail(size_t size);
+  // Remove any pending alloc failures.
+  static void ClearFails();
+
+  static void *amalloc(size_t size);
+  static void* arealloc(void *ptr, size_t size);
+  static void afree(void *ptr);
+ private:
+  static bool ShouldAllocFail(size_t size);
+  static unsigned long fails_;
+  static std::map<size_t, int> size_fails_;
+};
+
+// Test fixture that uses a default channel.
+class DefaultChannelTest : public LibraryTest {
+ public:
+  DefaultChannelTest() : channel_(nullptr) {
+    EXPECT_EQ(ARES_SUCCESS, ares_init(&channel_));
+    EXPECT_NE(nullptr, channel_);
+  }
+
+  ~DefaultChannelTest() {
+    ares_destroy(channel_);
+    channel_ = nullptr;
+  }
+
+  // Process all pending work on ares-owned file descriptors.
+  void Process();
+
+ protected:
+  ares_channel channel_;
+};
+
+// Mock DNS server to allow responses to be scripted by tests.
+class MockServer {
+ public:
+  MockServer(int port);
+  ~MockServer();
+
+  // Mock method indicating the processing of a particular <name, RRtype>
+  // request.
+  MOCK_METHOD2(OnRequest, void(const std::string& name, int rrtype));
+
+  // Set the reply to be sent next; the query ID field will be overwritten
+  // with the value from the request.
+  void SetReplyData(const std::vector<byte>& reply) { reply_ = reply; }
+  void SetReply(const DNSPacket* reply) { SetReplyData(reply->data()); }
+
+  // Process activity on the mock server's socket FD.
+  void Process(int fd);
+
+  int port() const { return port_; }
+  int sockfd() const { return sockfd_; }
+
+ private:
+  void ProcessRequest(struct sockaddr_storage* addr, int addrlen,
+                      int qid, const std::string& name, int rrtype);
+
+  int port_;
+  int sockfd_;
+  std::vector<byte> reply_;
+};
+
+// Test fixture that uses a mock DNS server.
+class MockChannelOptsTest : public LibraryTest {
+ public:
+  MockChannelOptsTest(struct ares_options* givenopts, int optmask);
+  ~MockChannelOptsTest();
+
+  // Process all pending work on ares-owned and mock-server-owned file descriptors.
+  void Process();
+
+ protected:
+  testing::NiceMock<MockServer> server_;
+  ares_channel channel_;
+};
+
+class MockChannelTest : public MockChannelOptsTest {
+ public:
+  MockChannelTest() : MockChannelOptsTest(nullptr, 0) {}
+};
+
+// gMock action to set the reply for a mock server.
+ACTION_P2(SetReplyData, mockserver, data) {
+  mockserver->SetReplyData(data);
+}
+ACTION_P2(SetReply, mockserver, reply) {
+  mockserver->SetReply(reply);
+}
+// gMock action to cancel a channel.
+ACTION_P2(CancelChannel, mockserver, channel) {
+  ares_cancel(channel);
+}
+
+// C++ wrapper for struct hostent.
+struct HostEnt {
+  HostEnt() : addrtype_(-1) {}
+  HostEnt(const struct hostent* hostent);
+  std::string name_;
+  std::vector<std::string> aliases_;
+  int addrtype_;  // AF_INET or AF_INET6
+  std::vector<std::string> addrs_;
+};
+std::ostream& operator<<(std::ostream& os, const HostEnt& result);
+
+// Structure that describes the result of an ares_host_callback invocation.
+struct HostResult {
+  // Whether the callback has been invoked.
+  bool done_;
+  // Explicitly provided result information.
+  int status_;
+  int timeouts_;
+  // Contents of the hostent structure, if provided.
+  HostEnt host_;
+};
+std::ostream& operator<<(std::ostream& os, const HostResult& result);
+
+// Structure that describes the result of an ares_callback invocation.
+struct SearchResult {
+  // Whether the callback has been invoked.
+  bool done_;
+  // Explicitly provided result information.
+  int status_;
+  int timeouts_;
+  std::vector<byte> data_;
+};
+std::ostream& operator<<(std::ostream& os, const SearchResult& result);
+
+// Structure that describes the result of an ares_nameinfo_callback invocation.
+struct NameInfoResult {
+  // Whether the callback has been invoked.
+  bool done_;
+  // Explicitly provided result information.
+  int status_;
+  int timeouts_;
+  std::string node_;
+  std::string service_;
+};
+std::ostream& operator<<(std::ostream& os, const NameInfoResult& result);
+
+// Standard implementation of ares callbacks that fill out the corresponding
+// structures.
+void HostCallback(void *data, int status, int timeouts,
+                  struct hostent *hostent);
+void SearchCallback(void *data, int status, int timeouts,
+                    unsigned char *abuf, int alen);
+void NameInfoCallback(void *data, int status, int timeouts,
+                      char *node, char *service);
+
+
+}  // namespace test
+}  // namespace ares
+
+#endif
--- a/test/buildconf
+++ b/test/buildconf
@ -0,0 +1,2 @@
+#!/bin/sh
+autoreconf -iv
--- a/test/configure.ac
+++ b/test/configure.ac
@ -0,0 +1,17 @@
+AC_PREREQ(2.57)
+AC_INIT([c-ares-test],[-],[-])
+AC_CONFIG_SRCDIR([ares-test.cc])
+AC_CONFIG_MACRO_DIR([../m4])
+
+AM_INIT_AUTOMAKE()
+
+dnl Checks for programs.
+AC_PROG_CXX
+AX_CXX_COMPILE_STDCXX_11([noext],[mandatory])
+LT_INIT
+AC_SUBST(LIBTOOL_DEPS)
+AX_PTHREAD
+AX_CODE_COVERAGE
+
+AC_CONFIG_FILES([Makefile])
+AC_OUTPUT
--- a/test/dns-proto-test.cc
+++ b/test/dns-proto-test.cc
@ -0,0 +1,131 @@
+#include "ares-test.h"
+#include "dns-proto.h"
+
+#include <vector>
+
+namespace ares {
+namespace test {
+
+TEST(DNSProto, EncodeQuestions) {
+  DNSPacket pkt;
+  pkt.set_qid(0x1234).set_response().set_aa()
+    .add_question(new DNSQuestion("example.com.", ns_t_a))
+    .add_question(new DNSQuestion("www.example.com", ns_t_aaaa, ns_c_chaos));
+
+  std::vector<byte> data = {
+    0x12, 0x34,  // qid
+    0x84, // response + query + AA + not-TC + not-RD
+    0x00, // not-RA + not-Z + not-AD + not-CD + rc=NoError
+    0x00, 0x02,  // num questions
+    0x00, 0x00,  // num answer RRs
+    0x00, 0x00,  // num authority RRs
+    0x00, 0x00,  // num additional RRs
+    // Question 1
+    0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x01,  // type A
+    0x00, 0x01,  // class IN
+    // Question 2
+    0x03, 'w', 'w', 'w',
+    0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x1C,  // type AAAA = 28
+    0x00, 0x03,  // class CHAOS = 3
+  };
+  EXPECT_EQ(data, pkt.data());
+}
+
+TEST(DNSProto, EncodeSingleNameAnswers) {
+  DNSPacket pkt;
+  pkt.qid_ = 0x1234;
+  pkt.response_ = true;
+  pkt.aa_ = true;
+  pkt.opcode_ = ns_o_query;
+  pkt.add_answer(new DNSCnameRR("example.com", 0x01020304, "other.com."));
+  pkt.add_auth(new DNSPtrRR("www.example.com", 0x01020304, "www.other.com"));
+
+  std::vector<byte> data = {
+    0x12, 0x34,  // qid
+    0x84, // response + query + AA + not-TC + not-RD
+    0x00, // not-RA + not-Z + not-AD + not-CD + rc=NoError
+    0x00, 0x00,  // num questions
+    0x00, 0x01,  // num answer RRs
+    0x00, 0x01,  // num authority RRs
+    0x00, 0x00,  // num additional RRs
+    // Answer 1
+    0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x05,  // RR type
+    0x00, 0x01,  // class IN
+    0x01, 0x02, 0x03, 0x04, // TTL
+    0x00, 0x0B,  // rdata length
+    0x05, 'o', 't', 'h', 'e', 'r',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    // Authority 1
+    0x03, 'w', 'w', 'w',
+    0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x0c,  // RR type
+    0x00, 0x01,  // class IN
+    0x01, 0x02, 0x03, 0x04, // TTL
+    0x00, 0x0F,  // rdata length
+    0x03, 'w', 'w', 'w',
+    0x05, 'o', 't', 'h', 'e', 'r',
+    0x03, 'c', 'o', 'm',
+    0x00,
+  };
+  EXPECT_EQ(data, pkt.data());
+}
+
+TEST(DNSProto, EncodeAddressAnswers) {
+  DNSPacket pkt;
+  pkt.qid_ = 0x1234;
+  pkt.response_ = true;
+  pkt.aa_ = true;
+  pkt.opcode_ = ns_o_query;
+  std::vector<byte> addrv4 = {0x02, 0x03, 0x04, 0x05};
+  pkt.add_answer(new DNSARR("example.com", 0x01020304, addrv4));
+  byte addrv6[16] = {0x01, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02, 0x02,
+                     0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04};
+  pkt.add_additional(new DNSAaaaRR("www.example.com", 0x01020304, addrv6, 16));
+
+  std::vector<byte> data = {
+    0x12, 0x34,  // qid
+    0x84, // response + query + AA + not-TC + not-RD
+    0x00, // not-RA + not-Z + not-AD + not-CD + rc=NoError
+    0x00, 0x00,  // num questions
+    0x00, 0x01,  // num answer RRs
+    0x00, 0x00,  // num authority RRs
+    0x00, 0x01,  // num additional RRs
+    // Answer 1
+    0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x01,  // RR type
+    0x00, 0x01,  // class IN
+    0x01, 0x02, 0x03, 0x04, // TTL
+    0x00, 0x04,  // rdata length
+    0x02, 0x03, 0x04, 0x05,
+    // Additional 1
+    0x03, 'w', 'w', 'w',
+    0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+    0x03, 'c', 'o', 'm',
+    0x00,
+    0x00, 0x1c,  // RR type
+    0x00, 0x01,  // class IN
+    0x01, 0x02, 0x03, 0x04, // TTL
+    0x00, 0x10,  // rdata length
+    0x01, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02, 0x02,
+    0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04
+  };
+  EXPECT_EQ(data, pkt.data());
+}
+
+
+}  // namespace test
+}  // namespace ares
--- a/test/dns-proto.cc
+++ b/test/dns-proto.cc
@ -0,0 +1,577 @@
+#include "dns-proto.h"
+
+// Include ares internal file for DNS protocol details
+#include "ares.h"
+#include "ares_dns.h"
+
+#include <sstream>
+
+namespace ares {
+
+std::string HexDump(std::vector<byte> data) {
+  std::stringstream ss;
+  for (size_t ii = 0; ii < data.size();  ii++) {
+    char buffer[2 + 1];
+    sprintf(buffer, "%02x", data[ii]);
+    ss << buffer;
+  }
+  return ss.str();
+}
+
+std::string HexDump(const byte *data, int len) {
+  return HexDump(std::vector<byte>(data, data + len));
+}
+
+std::string HexDump(const char *data, int len) {
+  return HexDump(reinterpret_cast<const byte*>(data), len);
+}
+
+std::string StatusToString(int status) {
+  switch (status) {
+  case ARES_SUCCESS: return "ARES_SUCCESS";
+  case ARES_ENODATA: return "ARES_ENODATA";
+  case ARES_EFORMERR: return "ARES_EFORMERR";
+  case ARES_ESERVFAIL: return "ARES_ESERVFAIL";
+  case ARES_ENOTFOUND: return "ARES_ENOTFOUND";
+  case ARES_ENOTIMP: return "ARES_ENOTIMP";
+  case ARES_EREFUSED: return "ARES_EREFUSED";
+  case ARES_EBADQUERY: return "ARES_EBADQUERY";
+  case ARES_EBADNAME: return "ARES_EBADNAME";
+  case ARES_EBADFAMILY: return "ARES_EBADFAMILY";
+  case ARES_EBADRESP: return "ARES_EBADRESP";
+  case ARES_ECONNREFUSED: return "ARES_ECONNREFUSED";
+  case ARES_ETIMEOUT: return "ARES_ETIMEOUT";
+  case ARES_EOF: return "ARES_EOF";
+  case ARES_EFILE: return "ARES_EFILE";
+  case ARES_ENOMEM: return "ARES_ENOMEM";
+  case ARES_EDESTRUCTION: return "ARES_EDESTRUCTION";
+  case ARES_EBADSTR: return "ARES_EBADSTR";
+  case ARES_EBADFLAGS: return "ARES_EBADFLAGS";
+  case ARES_ENONAME: return "ARES_ENONAME";
+  case ARES_EBADHINTS: return "ARES_EBADHINTS";
+  case ARES_ENOTINITIALIZED: return "ARES_ENOTINITIALIZED";
+  case ARES_ELOADIPHLPAPI: return "ARES_ELOADIPHLPAPI";
+  case ARES_EADDRGETNETWORKPARAMS: return "ARES_EADDRGETNETWORKPARAMS";
+  case ARES_ECANCELLED: return "ARES_ECANCELLED";
+  default: return "UNKNOWN";
+  }
+}
+
+std::string RcodeToString(int rcode) {
+  switch (rcode) {
+  case ns_r_noerror: return "NOERROR";
+  case ns_r_formerr: return "FORMERR";
+  case ns_r_servfail: return "SERVFAIL";
+  case ns_r_nxdomain: return "NXDOMAIN";
+  case ns_r_notimpl: return "NOTIMPL";
+  case ns_r_refused: return "REFUSED";
+  case ns_r_yxdomain: return "YXDOMAIN";
+  case ns_r_yxrrset: return "YXRRSET";
+  case ns_r_nxrrset: return "NXRRSET";
+  case ns_r_notauth: return "NOTAUTH";
+  case ns_r_notzone: return "NOTZONE";
+  case ns_r_badsig: return "BADSIG";
+  case ns_r_badkey: return "BADKEY";
+  case ns_r_badtime: return "BADTIME";
+  default: return "UNKNOWN";
+  }
+}
+
+std::string RRTypeToString(int rrtype) {
+  switch (rrtype) {
+  case ns_t_a: return "A";
+  case ns_t_ns: return "NS";
+  case ns_t_md: return "MD";
+  case ns_t_mf: return "MF";
+  case ns_t_cname: return "CNAME";
+  case ns_t_soa: return "SOA";
+  case ns_t_mb: return "MB";
+  case ns_t_mg: return "MG";
+  case ns_t_mr: return "MR";
+  case ns_t_null: return "NULL";
+  case ns_t_wks: return "WKS";
+  case ns_t_ptr: return "PTR";
+  case ns_t_hinfo: return "HINFO";
+  case ns_t_minfo: return "MINFO";
+  case ns_t_mx: return "MX";
+  case ns_t_txt: return "TXT";
+  case ns_t_rp: return "RP";
+  case ns_t_afsdb: return "AFSDB";
+  case ns_t_x25: return "X25";
+  case ns_t_isdn: return "ISDN";
+  case ns_t_rt: return "RT";
+  case ns_t_nsap: return "NSAP";
+  case ns_t_nsap_ptr: return "NSAP_PTR";
+  case ns_t_sig: return "SIG";
+  case ns_t_key: return "KEY";
+  case ns_t_px: return "PX";
+  case ns_t_gpos: return "GPOS";
+  case ns_t_aaaa: return "AAAA";
+  case ns_t_loc: return "LOC";
+  case ns_t_nxt: return "NXT";
+  case ns_t_eid: return "EID";
+  case ns_t_nimloc: return "NIMLOC";
+  case ns_t_srv: return "SRV";
+  case ns_t_atma: return "ATMA";
+  case ns_t_naptr: return "NAPTR";
+  case ns_t_kx: return "KX";
+  case ns_t_cert: return "CERT";
+  case ns_t_a6: return "A6";
+  case ns_t_dname: return "DNAME";
+  case ns_t_sink: return "SINK";
+  case ns_t_opt: return "OPT";
+  case ns_t_apl: return "APL";
+  case ns_t_ds: return "DS";
+  case ns_t_sshfp: return "SSHFP";
+  case ns_t_rrsig: return "RRSIG";
+  case ns_t_nsec: return "NSEC";
+  case ns_t_dnskey: return "DNSKEY";
+  case ns_t_tkey: return "TKEY";
+  case ns_t_tsig: return "TSIG";
+  case ns_t_ixfr: return "IXFR";
+  case ns_t_axfr: return "AXFR";
+  case ns_t_mailb: return "MAILB";
+  case ns_t_maila: return "MAILA";
+  case ns_t_any: return "ANY";
+  case ns_t_zxfr: return "ZXFR";
+  case ns_t_max: return "MAX";
+  default: return "UNKNOWN";
+  }
+}
+
+std::string ClassToString(int qclass) {
+  switch (qclass) {
+  case ns_c_in: return "IN";
+  case ns_c_chaos: return "CHAOS";
+  case ns_c_hs: return "HESIOD";
+  case ns_c_none: return "NONE";
+  case ns_c_any: return "ANY";
+  default: return "UNKNOWN";
+  }
+}
+
+std::string AddressToString(const byte* addr, int len) {
+  std::stringstream ss;
+  if (len == 4) {
+    char buffer[4*4 + 3 + 1];
+    sprintf(buffer, "%u.%u.%u.%u",
+            (unsigned char)addr[0],
+            (unsigned char)addr[1],
+            (unsigned char)addr[2],
+            (unsigned char)addr[3]);
+    ss << buffer;
+  } else if (len == 16) {
+    for (int ii = 0; ii < 16;  ii+=2) {
+      if (ii > 0) ss << ':';
+      char buffer[4 + 1];
+      sprintf(buffer, "%02x%02x", (unsigned char)addr[ii], (unsigned char)addr[ii+1]);
+      ss << buffer;
+    }
+  } else {
+    ss << "!" << HexDump(addr, len) << "!";
+  }
+  return ss.str();
+}
+
+std::string AddressToString(const char* addr, int len) {
+  return AddressToString(reinterpret_cast<const byte*>(addr), len);
+}
+
+std::string PacketToString(const std::vector<byte>& packet) {
+  const byte* data = packet.data();
+  int len = packet.size();
+  std::stringstream ss;
+  if (len < NS_HFIXEDSZ) {
+    ss << "(too short, len " << len << ")";
+    return ss.str();
+  }
+  ss << ((DNS_HEADER_QR(data) == 0) ? "REQ " : "RSP ");
+  switch (DNS_HEADER_OPCODE(data)) {
+  case ns_o_query: ss << "QRY "; break;
+  case ns_o_iquery: ss << "IQRY "; break;
+  case ns_o_status: ss << "STATUS "; break;
+  case ns_o_notify: ss << "NOTIFY "; break;
+  case ns_o_update: ss << "UPDATE "; break;
+  default: ss << "UNKNOWN(" << DNS_HEADER_OPCODE(data) << ") "; break;
+  }
+  if (DNS_HEADER_AA(data)) ss << "AA ";
+  if (DNS_HEADER_TC(data)) ss << "TC ";
+  if (DNS_HEADER_RD(data)) ss << "RD ";
+  if (DNS_HEADER_RA(data)) ss << "RA ";
+  if (DNS_HEADER_Z(data)) ss << "Z ";
+  if (DNS_HEADER_QR(data) == 1) ss << RcodeToString(DNS_HEADER_RCODE(data));
+
+  int nquestions = DNS_HEADER_QDCOUNT(data);
+  int nanswers = DNS_HEADER_ANCOUNT(data);
+  int nauths = DNS_HEADER_NSCOUNT(data);
+  int nadds = DNS_HEADER_ARCOUNT(data);
+
+  const byte* pq = data + NS_HFIXEDSZ;
+  len -= NS_HFIXEDSZ;
+  for (int ii = 0; ii < nquestions; ii++) {
+    ss << " Q:" << QuestionToString(packet, &pq, &len);
+  }
+  const byte* prr = pq;
+  for (int ii = 0; ii < nanswers; ii++) {
+    ss << " A:" << RRToString(packet, &prr, &len);
+  }
+  for (int ii = 0; ii < nauths; ii++) {
+    ss << " AUTH:" << RRToString(packet, &prr, &len);
+  }
+  for (int ii = 0; ii < nadds; ii++) {
+    ss << " ADD:" << RRToString(packet, &prr, &len);
+  }
+  return ss.str();
+}
+
+std::string QuestionToString(const std::vector<byte>& packet,
+                             const byte** data, int* len) {
+  std::stringstream ss;
+  ss << "{";
+  if (*len < NS_QFIXEDSZ) {
+    ss << "(too short, len " << *len << ")";
+    return ss.str();
+  }
+
+  char *name = nullptr;
+  long enclen;
+  ares_expand_name(*data, packet.data(), packet.size(), &name, &enclen);
+  *len -= enclen;
+  *data += enclen;
+  ss << "'" << name << "' ";
+  free(name);
+  if (*len < NS_QFIXEDSZ) {
+    ss << "(too short, len left " << *len << ")";
+    return ss.str();
+  }
+  ss << ClassToString(DNS_QUESTION_CLASS(*data)) << " ";
+  ss << RRTypeToString(DNS_QUESTION_TYPE(*data));
+  *data += NS_QFIXEDSZ;
+  *len -= NS_QFIXEDSZ;
+  ss << "}";
+  return ss.str();
+}
+
+std::string RRToString(const std::vector<byte>& packet,
+                       const byte** data, int* len) {
+  std::stringstream ss;
+  ss << "{";
+  if (*len < NS_RRFIXEDSZ) {
+    ss << "too short, len " << *len << ")";
+    return ss.str();
+  }
+
+  char *name = nullptr;
+  long enclen;
+  ares_expand_name(*data, packet.data(), packet.size(), &name, &enclen);
+  *len -= enclen;
+  *data += enclen;
+  ss << "'" << name << "' ";
+  free(name);
+  name = nullptr;
+
+  if (*len < NS_QFIXEDSZ) {
+    ss << "(too short, len left " << *len << ")";
+    return ss.str();
+  }
+  int rrtype = DNS_RR_TYPE(*data);
+  if (rrtype == ns_t_opt) {
+    ss << "MAXUDP=" << DNS_RR_CLASS(*data) << " ";
+    ss << RRTypeToString(rrtype) << " ";
+    ss << "RCODE2=" << DNS_RR_TTL(*data);
+  } else {
+    ss << ClassToString(DNS_RR_CLASS(*data)) << " ";
+    ss << RRTypeToString(rrtype) << " ";
+    ss << "TTL=" << DNS_RR_TTL(*data);
+  }
+  int rdatalen = DNS_RR_LEN(*data);
+
+  *data += NS_RRFIXEDSZ;
+  *len -= NS_RRFIXEDSZ;
+  switch (rrtype) {
+  case ns_t_a:
+  case ns_t_aaaa:
+    ss << " " << AddressToString(*data, rdatalen);
+    break;
+  case ns_t_txt: {
+    const byte* p = *data;
+    while (p < (*data + rdatalen)) {
+      int len = *p++;
+      std::string txt(p, p + len);
+      ss << " " << len << ":'" << txt << "'";
+      p += len;
+    }
+    break;
+  }
+  case ns_t_cname:
+  case ns_t_ns:
+  case ns_t_ptr:
+    ares_expand_name(*data, packet.data(), packet.size(), &name, &enclen);
+    ss << " '" << name << "'";
+    free(name);
+    break;
+  case ns_t_mx:
+    ares_expand_name(*data + 2, packet.data(), packet.size(), &name, &enclen);
+    ss << " " << DNS__16BIT(*data) << " '" << name << "'";
+    free(name);
+    break;
+  case ns_t_srv: {
+    const byte* p = *data;
+    unsigned long prio = DNS__16BIT(p);
+    unsigned long weight = DNS__16BIT(p + 2);
+    unsigned long port = DNS__16BIT(p + 4);
+    p += 6;
+    ares_expand_name(p, packet.data(), packet.size(), &name, &enclen);
+    ss << prio << " " << weight << " " << port << " '" << name << "'";
+    free(name);
+    break;
+  }
+  case ns_t_soa: {
+    const byte* p = *data;
+    ares_expand_name(p, packet.data(), packet.size(), &name, &enclen);
+    ss << " '" << name << "'";
+    free(name);
+    p += enclen;
+    ares_expand_name(p, packet.data(), packet.size(), &name, &enclen);
+    ss << " '" << name << "'";
+    free(name);
+    p += enclen;
+    unsigned long serial = DNS__32BIT(p);
+    unsigned long refresh = DNS__32BIT(p + 4);
+    unsigned long retry = DNS__32BIT(p + 8);
+    unsigned long expire = DNS__32BIT(p + 12);
+    unsigned long minimum = DNS__32BIT(p + 16);
+    ss << " " << serial << " " << refresh << " " << retry << " " << expire << " " << minimum;
+    break;
+  }
+  case ns_t_naptr: {
+    const byte* p = *data;
+    unsigned long order = DNS__16BIT(p);
+    unsigned long pref = DNS__16BIT(p + 2);
+    p += 4;
+    ss << order << " " << pref;
+
+    int len = *p++;
+    std::string flags(p, p + len);
+    ss << " " << flags;
+    p += len;
+
+    len = *p++;
+    std::string service(p, p + len);
+    ss << " '" << service << "'";
+    p += len;
+
+    len = *p++;
+    std::string regexp(p, p + len);
+    ss << " '" << regexp << "'";
+    p += len;
+
+    ares_expand_name(p, packet.data(), packet.size(), &name, &enclen);
+    ss << " '" << name << "'";
+    free(name);
+    p += enclen;
+    break;
+  }
+  default:
+    ss << " " << HexDump(*data, rdatalen);
+    break;
+  }
+  *data += rdatalen;
+  *len -= rdatalen;
+
+  ss << "}";
+  return ss.str();
+}
+
+namespace {
+
+void PushInt32(std::vector<byte>* data, int value) {
+  data->push_back((value & 0xff000000) >> 24);
+  data->push_back((value & 0x00ff0000) >> 16);
+  data->push_back((value & 0x0000ff00) >> 8);
+  data->push_back(value & 0x000000ff);
+}
+
+void PushInt16(std::vector<byte>* data, int value) {
+  data->push_back((value & 0xff00) >> 8);
+  data->push_back(value & 0x00ff);
+}
+
+std::vector<byte> EncodeString(const std::string& name) {
+  std::vector<byte> data;
+  std::stringstream ss(name);
+  std::string label;
+  // TODO: cope with escapes
+  while (std::getline(ss, label, '.')) {
+    data.push_back(label.length());
+    data.insert(data.end(), label.begin(), label.end());
+  }
+  data.push_back(0);
+  return data;
+}
+
+}  // namespace
+
+std::vector<byte> DNSQuestion::data() const {
+  std::vector<byte> data;
+  std::vector<byte> encname = EncodeString(name_);
+  data.insert(data.end(), encname.begin(), encname.end());
+  PushInt16(&data, rrtype_);
+  PushInt16(&data, qclass_);
+  return data;
+}
+
+std::vector<byte> DNSRR::data() const {
+  std::vector<byte> data = DNSQuestion::data();
+  PushInt32(&data, ttl_);
+  return data;
+}
+
+std::vector<byte> DNSSingleNameRR::data() const {
+  std::vector<byte> data = DNSRR::data();
+  std::vector<byte> encname = EncodeString(other_);
+  int len = encname.size();
+  PushInt16(&data, len);
+  data.insert(data.end(), encname.begin(), encname.end());
+  return data;
+}
+
+std::vector<byte> DNSTxtRR::data() const {
+  std::vector<byte> data = DNSRR::data();
+  int len = 0;
+  for (const std::string& txt : txt_) {
+    len += (1 + txt.size());
+  }
+  PushInt16(&data, len);
+  for (const std::string& txt : txt_) {
+    data.push_back(txt.size());
+    data.insert(data.end(), txt.begin(), txt.end());
+  }
+  return data;
+}
+
+std::vector<byte> DNSMxRR::data() const {
+  std::vector<byte> data = DNSRR::data();
+  std::vector<byte> encname = EncodeString(other_);
+  int len = 2 + encname.size();
+  PushInt16(&data, len);
+  PushInt16(&data, pref_);
+  data.insert(data.end(), encname.begin(), encname.end());
+  return data;
+}
+
+std::vector<byte> DNSSrvRR::data() const {
+  std::vector<byte> data = DNSRR::data();
+  std::vector<byte> encname = EncodeString(target_);
+  int len = 6 + encname.size();
+  PushInt16(&data, len);
+  PushInt16(&data, prio_);
+  PushInt16(&data, weight_);
+  PushInt16(&data, port_);
+  data.insert(data.end(), encname.begin(), encname.end());
+  return data;
+}
+
+std::vector<byte> DNSAddressRR::data() const {
+  std::vector<byte> data = DNSRR::data();
+  int len = addr_.size();
+  PushInt16(&data, len);
+  data.insert(data.end(), addr_.begin(), addr_.end());
+  return data;
+}
+
+std::vector<byte> DNSSoaRR::data() const {
+  std::vector<byte> data = DNSRR::data();
+  std::vector<byte> encname1 = EncodeString(nsname_);
+  std::vector<byte> encname2 = EncodeString(rname_);
+  int len = encname1.size() + encname2.size() + 5*4;
+  PushInt16(&data, len);
+  data.insert(data.end(), encname1.begin(), encname1.end());
+  data.insert(data.end(), encname2.begin(), encname2.end());
+  PushInt32(&data, serial_);
+  PushInt32(&data, refresh_);
+  PushInt32(&data, retry_);
+  PushInt32(&data, expire_);
+  PushInt32(&data, minimum_);
+  return data;
+}
+
+std::vector<byte> DNSOptRR::data() const {
+  std::vector<byte> data = DNSRR::data();
+  int len = 0;
+  for (const DNSOption& opt : opts_) {
+    len += (4 + opt.data_.size());
+  }
+  PushInt16(&data, len);
+  for (const DNSOption& opt : opts_) {
+    PushInt16(&data, opt.code_);
+    PushInt16(&data, opt.data_.size());
+    data.insert(data.end(), opt.data_.begin(), opt.data_.end());
+  }
+  return data;
+}
+
+std::vector<byte> DNSNaptrRR::data() const {
+  std::vector<byte> data = DNSRR::data();
+  std::vector<byte> encname = EncodeString(replacement_);
+  int len = (4 + 1 + flags_.size() + 1 + service_.size() + 1 + regexp_.size() + encname.size());
+  PushInt16(&data, len);
+  PushInt16(&data, order_);
+  PushInt16(&data, pref_);
+  data.push_back(flags_.size());
+  data.insert(data.end(), flags_.begin(), flags_.end());
+  data.push_back(service_.size());
+  data.insert(data.end(), service_.begin(), service_.end());
+  data.push_back(regexp_.size());
+  data.insert(data.end(), regexp_.begin(), regexp_.end());
+  data.insert(data.end(), encname.begin(), encname.end());
+  return data;
+}
+
+std::vector<byte> DNSPacket::data() const {
+  std::vector<byte> data;
+  PushInt16(&data, qid_);
+  byte b = 0x00;
+  if (response_) b |= 0x80;
+  b |= ((opcode_ & 0x0f) << 3);
+  if (aa_) b |= 0x04;
+  if (tc_) b |= 0x02;
+  if (rd_) b |= 0x01;
+  data.push_back(b);
+  b = 0x00;
+  if (ra_) b |= 0x80;
+  if (z_) b |= 0x40;
+  if (ad_) b |= 0x20;
+  if (cd_) b |= 0x10;
+  b |= (rcode_ & 0x0f);
+  data.push_back(b);
+
+  int count = questions_.size();
+  PushInt16(&data, count);
+  count = answers_.size();
+  PushInt16(&data, count);
+  count = auths_.size();
+  PushInt16(&data, count);
+  count = adds_.size();
+  PushInt16(&data, count);
+
+  for (const std::unique_ptr<DNSQuestion>& question : questions_) {
+    std::vector<byte> qdata = question->data();
+    data.insert(data.end(), qdata.begin(), qdata.end());
+  }
+  for (const std::unique_ptr<DNSRR>& rr : answers_) {
+    std::vector<byte> rrdata = rr->data();
+    data.insert(data.end(), rrdata.begin(), rrdata.end());
+  }
+  for (const std::unique_ptr<DNSRR>& rr : auths_) {
+    std::vector<byte> rrdata = rr->data();
+    data.insert(data.end(), rrdata.begin(), rrdata.end());
+  }
+  for (const std::unique_ptr<DNSRR>& rr : adds_) {
+    std::vector<byte> rrdata = rr->data();
+    data.insert(data.end(), rrdata.begin(), rrdata.end());
+  }
+  return data;
+}
+
+}  // namespace ares
--- a/test/dns-proto.h
+++ b/test/dns-proto.h
@ -0,0 +1,235 @@
+// -*- mode: c++ -*-
+#ifndef DNS_PROTO_H
+#define DNS_PROTO_H
+// Utilities for processing DNS packet contents
+
+// Include ares internal file for DNS protocol constants
+#include "nameser.h"
+
+#include <memory>
+#include <string>
+#include <vector>
+
+namespace ares {
+
+typedef unsigned char byte;
+
+std::string HexDump(std::vector<byte> data);
+std::string HexDump(const byte *data, int len);
+std::string HexDump(const char *data, int len);
+
+std::string StatusToString(int status);
+std::string RcodeToString(int rcode);
+std::string RRTypeToString(int rrtype);
+std::string ClassToString(int qclass);
+std::string AddressToString(const byte* addr, int len);
+std::string AddressToString(const char* addr, int len);
+
+// Convert DNS protocol data to strings.
+// Note that these functions are not defensive; they assume
+// a validly formatted input, and so should not be used on
+// externally-determined inputs.
+std::string PacketToString(const std::vector<byte>& packet);
+std::string QuestionToString(const std::vector<byte>& packet,
+                             const byte** data, int* len);
+std::string RRToString(const std::vector<byte>& packet,
+                       const byte** data, int* len);
+
+struct DNSQuestion {
+  DNSQuestion(const std::string& name, ns_type rrtype, ns_class qclass)
+    : name_(name), rrtype_(rrtype), qclass_(qclass) {}
+  DNSQuestion(const std::string& name, ns_type rrtype)
+    : name_(name), rrtype_(rrtype), qclass_(ns_c_in) {}
+  virtual std::vector<byte> data() const;
+  std::string name_;
+  ns_type rrtype_;
+  ns_class qclass_;
+};
+
+struct DNSRR : public DNSQuestion {
+  DNSRR(const std::string& name, ns_type rrtype, ns_class qclass, int ttl)
+    : DNSQuestion(name, rrtype, qclass), ttl_(ttl) {}
+  DNSRR(const std::string& name, ns_type rrtype, int ttl)
+    : DNSQuestion(name, rrtype), ttl_(ttl) {}
+  virtual std::vector<byte> data() const = 0;
+  int ttl_;
+};
+
+struct DNSAddressRR : public DNSRR {
+  DNSAddressRR(const std::string& name, ns_type rrtype, int ttl,
+               const byte* addr, int addrlen)
+    : DNSRR(name, rrtype, ttl), addr_(addr, addr + addrlen) {}
+  DNSAddressRR(const std::string& name, ns_type rrtype, int ttl,
+               const std::vector<byte>& addr)
+    : DNSRR(name, rrtype, ttl), addr_(addr) {}
+  virtual std::vector<byte> data() const;
+  std::vector<byte> addr_;
+};
+
+struct DNSARR : public DNSAddressRR {
+  DNSARR(const std::string& name, int ttl, const byte* addr, int addrlen)
+    : DNSAddressRR(name, ns_t_a, ttl, addr, addrlen) {}
+  DNSARR(const std::string& name, int ttl, const std::vector<byte>& addr)
+    : DNSAddressRR(name, ns_t_a, ttl, addr) {}
+};
+
+struct DNSAaaaRR : public DNSAddressRR {
+  DNSAaaaRR(const std::string& name, int ttl, const byte* addr, int addrlen)
+    : DNSAddressRR(name, ns_t_aaaa, ttl, addr, addrlen) {}
+  DNSAaaaRR(const std::string& name, int ttl, const std::vector<byte>& addr)
+    : DNSAddressRR(name, ns_t_aaaa, ttl, addr) {}
+};
+
+struct DNSSingleNameRR : public DNSRR {
+  DNSSingleNameRR(const std::string& name, ns_type rrtype, int ttl,
+                  const std::string& other)
+    : DNSRR(name, rrtype, ttl), other_(other) {}
+  virtual std::vector<byte> data() const;
+  std::string other_;
+};
+
+struct DNSCnameRR : public DNSSingleNameRR {
+  DNSCnameRR(const std::string& name, int ttl, const std::string& other)
+    : DNSSingleNameRR(name, ns_t_cname, ttl, other) {}
+};
+
+struct DNSNsRR : public DNSSingleNameRR {
+  DNSNsRR(const std::string& name, int ttl, const std::string& other)
+    : DNSSingleNameRR(name, ns_t_ns, ttl, other) {}
+};
+
+struct DNSPtrRR : public DNSSingleNameRR {
+  DNSPtrRR(const std::string& name, int ttl, const std::string& other)
+    : DNSSingleNameRR(name, ns_t_ptr, ttl, other) {}
+};
+
+struct DNSTxtRR : public DNSRR {
+  DNSTxtRR(const std::string& name, int ttl, const std::vector<std::string>& txt)
+    : DNSRR(name, ns_t_txt, ttl), txt_(txt) {}
+  virtual std::vector<byte> data() const;
+  std::vector<std::string> txt_;
+};
+
+struct DNSMxRR : public DNSRR {
+  DNSMxRR(const std::string& name, int ttl, int pref, const std::string& other)
+    : DNSRR(name, ns_t_mx, ttl), pref_(pref), other_(other) {}
+  virtual std::vector<byte> data() const;
+  int pref_;
+  std::string other_;
+};
+
+struct DNSSrvRR : public DNSRR {
+  DNSSrvRR(const std::string& name, int ttl,
+           int prio, int weight, int port, const std::string& target)
+    : DNSRR(name, ns_t_srv, ttl), prio_(prio), weight_(weight), port_(port), target_(target) {}
+  virtual std::vector<byte> data() const;
+  int prio_;
+  int weight_;
+  int port_;
+  std::string target_;
+};
+
+struct DNSSoaRR : public DNSRR {
+  DNSSoaRR(const std::string& name, int ttl,
+           const std::string& nsname, const std::string& rname,
+           int serial, int refresh, int retry, int expire, int minimum)
+    : DNSRR(name, ns_t_soa, ttl), nsname_(nsname), rname_(rname),
+      serial_(serial), refresh_(refresh), retry_(retry),
+      expire_(expire), minimum_(minimum) {}
+  virtual std::vector<byte> data() const;
+  std::string nsname_;
+  std::string rname_;
+  int serial_;
+  int refresh_;
+  int retry_;
+  int expire_;
+  int minimum_;
+};
+
+struct DNSNaptrRR : public DNSRR {
+  DNSNaptrRR(const std::string& name, int ttl,
+             int order, int pref,
+             const std::string& flags,
+             const std::string& service,
+             const std::string& regexp,
+             const std::string& replacement)
+    : DNSRR(name, ns_t_naptr, ttl), order_(order), pref_(pref),
+      flags_(flags), service_(service), regexp_(regexp), replacement_(replacement) {}
+  virtual std::vector<byte> data() const;
+  int order_;
+  int pref_;
+  std::string flags_;
+  std::string service_;
+  std::string regexp_;
+  std::string replacement_;
+};
+
+struct DNSOption {
+  int code_;
+  std::vector<byte> data_;
+};
+
+struct DNSOptRR : public DNSRR {
+  DNSOptRR(int extrcode, int udpsize)
+    : DNSRR("", ns_t_opt, static_cast<ns_class>(udpsize), extrcode) {}
+  virtual std::vector<byte> data() const;
+  std::vector<DNSOption> opts_;
+};
+
+struct DNSPacket {
+  DNSPacket()
+    : qid_(0), response_(false), opcode_(ns_o_query),
+      aa_(false), tc_(false), rd_(false), ra_(false),
+      z_(false), ad_(false), cd_(false), rcode_(ns_r_noerror) {}
+  // Convenience functions that take ownership of given pointers.
+  DNSPacket& add_question(DNSQuestion *q) {
+    questions_.push_back(std::unique_ptr<DNSQuestion>(q));
+    return *this;
+  }
+  DNSPacket& add_answer(DNSRR *q) {
+    answers_.push_back(std::unique_ptr<DNSRR>(q));
+    return *this;
+  }
+  DNSPacket& add_auth(DNSRR *q) {
+    auths_.push_back(std::unique_ptr<DNSRR>(q));
+    return *this;
+  }
+  DNSPacket& add_additional(DNSRR *q) {
+    adds_.push_back(std::unique_ptr<DNSRR>(q));
+    return *this;
+  }
+  // Chainable setters.
+  DNSPacket& set_qid(int qid) { qid_ = qid; return *this; }
+  DNSPacket& set_response(bool v = true) { response_ = v; return *this; }
+  DNSPacket& set_aa(bool v = true) { aa_ = v; return *this; }
+  DNSPacket& set_tc(bool v = true) { tc_ = v; return *this; }
+  DNSPacket& set_rd(bool v = true) { rd_ = v; return *this; }
+  DNSPacket& set_ra(bool v = true) { ra_ = v; return *this; }
+  DNSPacket& set_z(bool v = true) { z_ = v; return *this; }
+  DNSPacket& set_ad(bool v = true) { ad_ = v; return *this; }
+  DNSPacket& set_cd(bool v = true) { cd_ = v; return *this; }
+  DNSPacket& set_rcode(ns_rcode rcode) { rcode_ = rcode; return *this; }
+
+  // Return the encoded packet.
+  std::vector<byte> data() const;
+
+  int qid_;
+  bool response_;
+  ns_opcode opcode_;
+  bool aa_;
+  bool tc_;
+  bool rd_;
+  bool ra_;
+  bool z_;
+  bool ad_;
+  bool cd_;
+  ns_rcode rcode_;
+  std::vector<std::unique_ptr<DNSQuestion>> questions_;
+  std::vector<std::unique_ptr<DNSRR>> answers_;
+  std::vector<std::unique_ptr<DNSRR>> auths_;
+  std::vector<std::unique_ptr<DNSRR>> adds_;
+};
+
+}  // namespace ares
+
+#endif
--- a/test/fuzzinput/answer_a
+++ b/test/fuzzinput/answer_a
--- a/test/fuzzinput/answer_aaaa
+++ b/test/fuzzinput/answer_aaaa