diff --git a/conformance/conformance_test.cc b/conformance/conformance_test.cc
new file mode 100644
index 0000000..ee75031
--- /dev/null
+++ b/conformance/conformance_test.cc
@@ -0,0 +1,395 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <errno.h>
+#include <stdarg.h>
+#include <unistd.h>
+#include <string>
+
+#include "conformance.pb.h"
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/wire_format_lite.h>
+
+using conformance::ConformanceRequest;
+using conformance::ConformanceResponse;
+using conformance::TestAllTypes;
+using google::protobuf::Descriptor;
+using google::protobuf::FieldDescriptor;
+using google::protobuf::internal::WireFormatLite;
+using std::string;
+
+int write_fd;
+int read_fd;
+int successes;
+int failures;
+bool verbose = false;
+
+string Escape(const string& str) {
+  // TODO.
+  return str;
+}
+
+#define STRINGIFY(x) #x
+#define TOSTRING(x) STRINGIFY(x)
+#define CHECK_SYSCALL(call) \
+  if (call < 0) { \
+    perror(#call " " __FILE__ ":" TOSTRING(__LINE__)); \
+    exit(1); \
+  }
+
+// TODO(haberman): make this work on Windows, instead of using these
+// UNIX-specific APIs.
+//
+// There is a platform-agnostic API in
+//    src/google/protobuf/compiler/subprocess.h
+//
+// However that API only supports sending a single message to the subprocess.
+// We really want to be able to send messages and receive responses one at a
+// time:
+//
+// 1. Spawning a new process for each test would take way too long for thousands
+//    of tests and subprocesses like java that can take 100ms or more to start
+//    up.
+//
+// 2. Sending all the tests in one big message and receiving all results in one
+//    big message would take away our visibility about which test(s) caused a
+//    crash or other fatal error.  It would also give us only a single failure
+//    instead of all of them.
+void SpawnTestProgram(char *executable) {
+  int toproc_pipe_fd[2];
+  int fromproc_pipe_fd[2];
+  if (pipe(toproc_pipe_fd) < 0 || pipe(fromproc_pipe_fd) < 0) {
+    perror("pipe");
+    exit(1);
+  }
+
+  pid_t pid = fork();
+  if (pid < 0) {
+    perror("fork");
+    exit(1);
+  }
+
+  if (pid) {
+    // Parent.
+    CHECK_SYSCALL(close(toproc_pipe_fd[0]));
+    CHECK_SYSCALL(close(fromproc_pipe_fd[1]));
+    write_fd = toproc_pipe_fd[1];
+    read_fd = fromproc_pipe_fd[0];
+  } else {
+    // Child.
+    CHECK_SYSCALL(close(STDIN_FILENO));
+    CHECK_SYSCALL(close(STDOUT_FILENO));
+    CHECK_SYSCALL(dup2(toproc_pipe_fd[0], STDIN_FILENO));
+    CHECK_SYSCALL(dup2(fromproc_pipe_fd[1], STDOUT_FILENO));
+
+    CHECK_SYSCALL(close(toproc_pipe_fd[0]));
+    CHECK_SYSCALL(close(fromproc_pipe_fd[1]));
+    CHECK_SYSCALL(close(toproc_pipe_fd[1]));
+    CHECK_SYSCALL(close(fromproc_pipe_fd[0]));
+
+    char *const argv[] = {executable, NULL};
+    CHECK_SYSCALL(execv(executable, argv));  // Never returns.
+  }
+}
+
+/* Invoking of tests **********************************************************/
+
+void ReportSuccess() {
+  successes++;
+}
+
+void ReportFailure(const char *fmt, ...) {
+  va_list args;
+  va_start(args, fmt);
+  vfprintf(stderr, fmt, args);
+  va_end(args);
+  failures++;
+}
+
+void CheckedWrite(int fd, const void *buf, size_t len) {
+  if (write(fd, buf, len) != len) {
+    GOOGLE_LOG(FATAL) << "Error writing to test program: " << strerror(errno);
+  }
+}
+
+void CheckedRead(int fd, void *buf, size_t len) {
+  size_t ofs = 0;
+  while (len > 0) {
+    ssize_t bytes_read = read(fd, (char*)buf + ofs, len);
+
+    if (bytes_read == 0) {
+      GOOGLE_LOG(FATAL) << "Unexpected EOF from test program";
+    } else if (bytes_read < 0) {
+      GOOGLE_LOG(FATAL) << "Error reading from test program: " << strerror(errno);
+    }
+
+    len -= bytes_read;
+    ofs += bytes_read;
+  }
+}
+
+void RunTest(const ConformanceRequest& request, ConformanceResponse* response) {
+  string serialized;
+  request.SerializeToString(&serialized);
+  uint32_t len = serialized.size();
+  CheckedWrite(write_fd, &len, sizeof(uint32_t));
+  CheckedWrite(write_fd, serialized.c_str(), serialized.size());
+  CheckedRead(read_fd, &len, sizeof(uint32_t));
+  serialized.resize(len);
+  CheckedRead(read_fd, (void*)serialized.c_str(), len);
+  if (!response->ParseFromString(serialized)) {
+    GOOGLE_LOG(FATAL) << "Could not parse response proto from tested process.";
+  }
+
+  if (verbose) {
+    fprintf(stderr, "conformance_test: request=%s, response=%s\n",
+            request.ShortDebugString().c_str(),
+            response->ShortDebugString().c_str());
+  }
+}
+
+void DoExpectParseFailureForProto(const string& proto, int line) {
+  ConformanceRequest request;
+  ConformanceResponse response;
+  request.set_protobuf_payload(proto);
+
+  // We don't expect output, but if the program erroneously accepts the protobuf
+  // we let it send its response as this.  We must not leave it unspecified.
+  request.set_requested_output(ConformanceRequest::PROTOBUF);
+
+  RunTest(request, &response);
+  if (response.result_case() == ConformanceResponse::kParseError) {
+    ReportSuccess();
+  } else {
+    ReportFailure("Should have failed, but didn't. Line: %d, Request: %s, "
+                  "response: %s\n",
+                  line,
+                  request.ShortDebugString().c_str(),
+                  response.ShortDebugString().c_str());
+  }
+}
+
+// Expect that this precise protobuf will cause a parse error.
+#define ExpectParseFailureForProto(proto) DoExpectParseFailureForProto(proto, __LINE__)
+
+// Expect that this protobuf will cause a parse error, even if it is followed
+// by valid protobuf data.  We can try running this twice: once with this
+// data verbatim and once with this data followed by some valid data.
+//
+// TODO(haberman): implement the second of these.
+#define ExpectHardParseFailureForProto(proto) DoExpectParseFailureForProto(proto, __LINE__)
+
+
+/* Routines for building arbitrary protos *************************************/
+
+// We would use CodedOutputStream except that we want more freedom to build
+// arbitrary protos (even invalid ones).
+
+const string empty;
+
+string cat(const string& a, const string& b,
+           const string& c = empty,
+           const string& d = empty,
+           const string& e = empty,
+           const string& f = empty,
+           const string& g = empty,
+           const string& h = empty,
+           const string& i = empty,
+           const string& j = empty,
+           const string& k = empty,
+           const string& l = empty) {
+  string ret;
+  ret.reserve(a.size() + b.size() + c.size() + d.size() + e.size() + f.size() +
+              g.size() + h.size() + i.size() + j.size() + k.size() + l.size());
+  ret.append(a);
+  ret.append(b);
+  ret.append(c);
+  ret.append(d);
+  ret.append(e);
+  ret.append(f);
+  ret.append(g);
+  ret.append(h);
+  ret.append(i);
+  ret.append(j);
+  ret.append(k);
+  ret.append(l);
+  return ret;
+}
+
+// The maximum number of bytes that it takes to encode a 64-bit varint.
+#define VARINT_MAX_LEN 10
+
+size_t vencode64(uint64_t val, char *buf) {
+  if (val == 0) { buf[0] = 0; return 1; }
+  size_t i = 0;
+  while (val) {
+    uint8_t byte = val & 0x7fU;
+    val >>= 7;
+    if (val) byte |= 0x80U;
+    buf[i++] = byte;
+  }
+  return i;
+}
+
+string varint(uint64_t x) {
+  char buf[VARINT_MAX_LEN];
+  size_t len = vencode64(x, buf);
+  return string(buf, len);
+}
+
+// TODO: proper byte-swapping for big-endian machines.
+string fixed32(void *data) { return string(static_cast<char*>(data), 4); }
+string fixed64(void *data) { return string(static_cast<char*>(data), 8); }
+
+string delim(const string& buf) { return cat(varint(buf.size()), buf); }
+string uint32(uint32_t u32) { return fixed32(&u32); }
+string uint64(uint64_t u64) { return fixed64(&u64); }
+string flt(float f) { return fixed32(&f); }
+string dbl(double d) { return fixed64(&d); }
+string zz32(int32_t x) { return varint(WireFormatLite::ZigZagEncode32(x)); }
+string zz64(int64_t x) { return varint(WireFormatLite::ZigZagEncode64(x)); }
+
+string tag(uint32_t fieldnum, char wire_type) {
+  return varint((fieldnum << 3) | wire_type);
+}
+
+string submsg(uint32_t fn, const string& buf) {
+  return cat( tag(fn, WireFormatLite::WIRETYPE_LENGTH_DELIMITED), delim(buf) );
+}
+
+#define UNKNOWN_FIELD 666
+
+uint32_t GetFieldNumberForType(WireFormatLite::FieldType type, bool repeated) {
+  const Descriptor* d = TestAllTypes().GetDescriptor();
+  for (int i = 0; i < d->field_count(); i++) {
+    const FieldDescriptor* f = d->field(i);
+    if (static_cast<WireFormatLite::FieldType>(f->type()) == type &&
+        f->is_repeated() == repeated) {
+      return f->number();
+    }
+  }
+  GOOGLE_LOG(FATAL) << "Couldn't find field with type " << (int)type;
+  return 0;
+}
+
+void TestPrematureEOFForType(WireFormatLite::FieldType type) {
+  // Incomplete values for each wire type.
+  static const string incompletes[6] = {
+    string("\x80"),     // VARINT
+    string("abcdefg"),  // 64BIT
+    string("\x80"),     // DELIMITED (partial length)
+    string(),           // START_GROUP (no value required)
+    string(),           // END_GROUP (no value required)
+    string("abc")       // 32BIT
+  };
+
+  uint32_t fieldnum = GetFieldNumberForType(type, false);
+  uint32_t rep_fieldnum = GetFieldNumberForType(type, true);
+  WireFormatLite::WireType wire_type =
+      WireFormatLite::WireTypeForFieldType(type);
+  const string& incomplete = incompletes[wire_type];
+
+  // EOF before a known non-repeated value.
+  ExpectParseFailureForProto(tag(fieldnum, wire_type));
+
+  // EOF before a known repeated value.
+  ExpectParseFailureForProto(tag(rep_fieldnum, wire_type));
+
+  // EOF before an unknown value.
+  ExpectParseFailureForProto(tag(UNKNOWN_FIELD, wire_type));
+
+  // EOF inside a known non-repeated value.
+  ExpectParseFailureForProto(
+      cat( tag(fieldnum, wire_type), incomplete ));
+
+  // EOF inside a known repeated value.
+  ExpectParseFailureForProto(
+      cat( tag(rep_fieldnum, wire_type), incomplete ));
+
+  // EOF inside an unknown value.
+  ExpectParseFailureForProto(
+      cat( tag(UNKNOWN_FIELD, wire_type), incomplete ));
+
+  if (wire_type == WireFormatLite::WIRETYPE_LENGTH_DELIMITED) {
+    // EOF in the middle of delimited data for known non-repeated value.
+    ExpectParseFailureForProto(
+        cat( tag(fieldnum, wire_type), varint(1) ));
+
+    // EOF in the middle of delimited data for known repeated value.
+    ExpectParseFailureForProto(
+        cat( tag(rep_fieldnum, wire_type), varint(1) ));
+
+    // EOF in the middle of delimited data for unknown value.
+    ExpectParseFailureForProto(
+        cat( tag(UNKNOWN_FIELD, wire_type), varint(1) ));
+
+    if (type == WireFormatLite::TYPE_MESSAGE) {
+      // Submessage ends in the middle of a value.
+      string incomplete_submsg =
+          cat( tag(WireFormatLite::TYPE_INT32, WireFormatLite::WIRETYPE_VARINT),
+                incompletes[WireFormatLite::WIRETYPE_VARINT] );
+      ExpectHardParseFailureForProto(
+          cat( tag(fieldnum, WireFormatLite::WIRETYPE_LENGTH_DELIMITED),
+               varint(incomplete_submsg.size()),
+               incomplete_submsg ));
+    }
+  } else if (type != WireFormatLite::TYPE_GROUP) {
+    // Non-delimited, non-group: eligible for packing.
+
+    // Packed region ends in the middle of a value.
+    ExpectHardParseFailureForProto(
+        cat( tag(rep_fieldnum, WireFormatLite::WIRETYPE_LENGTH_DELIMITED),
+             varint(incomplete.size()),
+             incomplete ));
+
+    // EOF in the middle of packed region.
+    ExpectParseFailureForProto(
+        cat( tag(rep_fieldnum, WireFormatLite::WIRETYPE_LENGTH_DELIMITED),
+             varint(1) ));
+  }
+}
+
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    fprintf(stderr, "Usage: conformance_test <test-program>\n");
+    exit(1);
+  }
+
+  SpawnTestProgram(argv[1]);
+
+  for (int i = 1; i <= FieldDescriptor::MAX_TYPE; i++) {
+    TestPrematureEOFForType(static_cast<WireFormatLite::FieldType>(i));
+  }
+
+  fprintf(stderr, "conformance_test: completed %d tests for %s, %d successes, "
+                  "%d failures.\n", successes + failures, argv[1], successes,
+                                     failures);
+}