Index: unittests/CMakeLists.txt
===================================================================
--- unittests/CMakeLists.txt
+++ unittests/CMakeLists.txt
@@ -68,9 +68,10 @@
 add_subdirectory(Symbol)
 add_subdirectory(SymbolFile)
 add_subdirectory(Target)
+add_subdirectory(tools)
 add_subdirectory(UnwindAssembly)
 add_subdirectory(Utility)
 
 if(LLDB_CAN_USE_DEBUGSERVER)
   add_subdirectory(debugserver)
-endif()
\ No newline at end of file
+endif()
Index: unittests/tools/CMakeLists.txt
===================================================================
--- /dev/null
+++ unittests/tools/CMakeLists.txt
@@ -0,0 +1 @@
+add_subdirectory(lldb-server)
Index: unittests/tools/lldb-server/CMakeLists.txt
===================================================================
--- /dev/null
+++ unittests/tools/lldb-server/CMakeLists.txt
@@ -0,0 +1,13 @@
+function(add_lldb_test_executable test_name)
+  set(EXCLUDE_FROM_ALL ON)
+  add_llvm_executable(${test_name} NO_INSTALL_RPATH ${ARGN})
+  set(outdir ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR})
+  set_output_directory(${test_name} BINARY_DIR ${outdir} LIBRARY_DIR ${outdir})
+endfunction()
+
+add_lldb_test_executable(thread_inferior inferior/thread_inferior.cpp)
+
+add_definitions(-DLLDB_SERVER="$<TARGET_FILE:lldb-server>")
+add_definitions(-DTHREAD_INFERIOR="${CMAKE_CURRENT_BINARY_DIR}/thread_inferior")
+add_subdirectory(tests)
+add_dependencies(LLDBServerTests thread_inferior)
Index: unittests/tools/lldb-server/inferior/thread_inferior.cpp
===================================================================
--- /dev/null
+++ unittests/tools/lldb-server/inferior/thread_inferior.cpp
@@ -0,0 +1,39 @@
+//===-- thread_inferior.cpp -------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include <atomic>
+#include <chrono>
+#include <string>
+#include <thread>
+#include <vector>
+#include "llvm/Support/Compiler.h"
+
+int main(int argc, char* argv[]) {
+  int thread_count = 2;
+  if (argc > 1) {
+    thread_count = std::stoi(argv[1], nullptr, 10);
+  }
+
+  std::atomic<bool> delay(true);
+  std::vector<std::thread> threads;
+  for (int i = 0; i < thread_count; i++) {
+    threads.push_back(std::thread([&delay] {
+      while (delay.load())
+        std::this_thread::sleep_for(std::chrono::seconds(1));
+    }));
+  }
+
+  LLVM_BUILTIN_DEBUGTRAP;
+  delay.store(false);
+  for (std::thread& t : threads) {
+    t.join();
+  }
+
+  return 0;
+}
Index: unittests/tools/lldb-server/tests/CMakeLists.txt
===================================================================
--- /dev/null
+++ unittests/tools/lldb-server/tests/CMakeLists.txt
@@ -0,0 +1,15 @@
+add_lldb_unittest(LLDBServerTests
+  TestClient.cpp
+  MessageObjects.cpp
+  ThreadIdsInJstopinfoTest.cpp
+
+  LINK_LIBS
+    lldbHost
+    lldbCore
+    lldbInterpreter
+    lldbTarget
+    lldbPluginPlatformLinux
+    lldbPluginProcessGDBRemote
+  LINK_COMPONENTS
+    Support
+  )
Index: unittests/tools/lldb-server/tests/MessageObjects.h
===================================================================
--- /dev/null
+++ unittests/tools/lldb-server/tests/MessageObjects.h
@@ -0,0 +1,102 @@
+//===-- MessageObjects.h ----------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/lldb-types.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/Support/Endian.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/FormatVariadic.h"
+#include <string>
+
+namespace llgs_tests {
+class ThreadInfo;
+typedef llvm::DenseMap<uint64_t, ThreadInfo> ThreadInfoMap;
+typedef llvm::DenseMap<uint64_t, uint64_t> U64Map;
+typedef llvm::DenseMap<unsigned int, std::string> RegisterMap;
+
+class ProcessInfo {
+public:
+  static llvm::Expected<ProcessInfo> Create(llvm::StringRef response);
+  lldb::pid_t GetPid() const;
+  llvm::support::endianness GetEndian() const;
+
+private:
+  ProcessInfo() = default;
+  lldb::pid_t pid;
+  lldb::pid_t parent_pid;
+  uint32_t real_uid;
+  uint32_t real_gid;
+  uint32_t effective_uid;
+  uint32_t effective_gid;
+  std::string triple;
+  llvm::SmallString<16> ostype;
+  llvm::support::endianness endian;
+  unsigned int ptrsize;
+};
+
+class ThreadInfo {
+public:
+  ThreadInfo() = default;
+  ThreadInfo(llvm::StringRef name, llvm::StringRef reason,
+             const RegisterMap &registers, unsigned int signal);
+
+  llvm::StringRef ReadRegister(unsigned int register_id) const;
+  bool ReadRegisterAsUint64(unsigned int register_id, uint64_t &value) const;
+
+private:
+  std::string name;
+  std::string reason;
+  RegisterMap registers;
+  unsigned int signal;
+};
+
+class JThreadsInfo {
+public:
+  static llvm::Expected<JThreadsInfo> Create(llvm::StringRef response,
+                                             llvm::support::endianness endian);
+
+  const ThreadInfoMap &GetThreadInfos() const;
+
+private:
+  JThreadsInfo() = default;
+  ThreadInfoMap thread_infos;
+};
+
+class StopReply {
+public:
+  static llvm::Expected<StopReply> Create(llvm::StringRef response,
+                                          llvm::support::endianness endian);
+  const U64Map &GetThreadPcs() const;
+
+private:
+  StopReply() = default;
+  void ParseResponse(llvm::StringRef response,
+                     llvm::support::endianness endian);
+  unsigned int signal;
+  lldb::tid_t thread;
+  std::string name;
+  U64Map thread_pcs;
+  RegisterMap registers;
+  std::string reason;
+};
+
+// Common functions for parsing packet data.
+llvm::Expected<llvm::StringMap<llvm::StringRef>>
+SplitPairList(llvm::StringRef caller, llvm::StringRef s);
+
+template <typename... Args>
+llvm::Error make_parsing_error(llvm::StringRef format, Args &&... args) {
+  std::string error =
+      "Unable to parse " +
+      llvm::formatv(format.data(), std::forward<Args>(args)...).str();
+  return llvm::make_error<llvm::StringError>(error,
+                                             llvm::inconvertibleErrorCode());
+}
+} // namespace llgs_tests
Index: unittests/tools/lldb-server/tests/MessageObjects.cpp
===================================================================
--- /dev/null
+++ unittests/tools/lldb-server/tests/MessageObjects.cpp
@@ -0,0 +1,206 @@
+//===-- MessageObjects.cpp --------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MessageObjects.h"
+#include "lldb/Core/StructuredData.h"
+#include "llvm/ADT/StringExtras.h"
+#include "gtest/gtest.h"
+
+using namespace lldb_private;
+using namespace llvm;
+using namespace llvm::support;
+namespace llgs_tests {
+
+Expected<ProcessInfo> ProcessInfo::Create(StringRef response) {
+  ProcessInfo process_info;
+  auto elements_or_error = SplitPairList("ProcessInfo", response);
+  if (!elements_or_error) return elements_or_error.takeError();
+
+  auto &elements = *elements_or_error;
+  if (elements["pid"].getAsInteger(16, process_info.pid))
+    return make_parsing_error("ProcessInfo: pid");
+  if (elements["parent-pid"].getAsInteger(16, process_info.parent_pid))
+    return make_parsing_error("ProcessInfo: parent-pid");
+  if (elements["real-uid"].getAsInteger(16, process_info.real_uid))
+    return make_parsing_error("ProcessInfo: real-uid");
+  if (elements["real-gid"].getAsInteger(16, process_info.real_gid))
+    return make_parsing_error("ProcessInfo: real-uid");
+  if (elements["effective-uid"].getAsInteger(16, process_info.effective_uid))
+    return make_parsing_error("ProcessInfo: effective-uid");
+  if (elements["effective-gid"].getAsInteger(16, process_info.effective_gid))
+    return make_parsing_error("ProcessInfo: effective-gid");
+  if (elements["ptrsize"].getAsInteger(10, process_info.ptrsize))
+    return make_parsing_error("ProcessInfo: ptrsize");
+
+  process_info.triple = fromHex(elements["triple"]);
+  StringRef endian_str = elements["endian"];
+  if (endian_str == "little")
+    process_info.endian = support::little;
+  else if (endian_str == "big")
+    process_info.endian = support::big;
+  else
+    return make_parsing_error("ProcessInfo: endian");
+
+  return process_info;
+}
+
+lldb::pid_t ProcessInfo::GetPid() const { return pid; }
+
+endianness ProcessInfo::GetEndian() const { return endian; }
+
+//====== ThreadInfo ============================================================
+ThreadInfo::ThreadInfo(StringRef name, StringRef reason,
+                       const RegisterMap &registers, unsigned int signal)
+    : name(name.str()), reason(reason.str()), registers(registers),
+      signal(signal) {}
+
+StringRef ThreadInfo::ReadRegister(unsigned int register_id) const {
+  return registers.lookup(register_id);
+}
+
+bool ThreadInfo::ReadRegisterAsUint64(unsigned int register_id,
+                                      uint64_t &value) const {
+  StringRef value_str(registers.lookup(register_id));
+  if (value_str.getAsInteger(16, value)) {
+    GTEST_LOG_(ERROR)
+        << formatv("ThreadInfo: Unable to parse register value at {0}.",
+                   register_id)
+               .str();
+    return false;
+  }
+
+  sys::swapByteOrder(value);
+  return true;
+}
+
+//====== JThreadsInfo ==========================================================
+Expected<JThreadsInfo> JThreadsInfo::Create(StringRef response,
+                                            endianness endian) {
+  JThreadsInfo jthreads_info;
+
+  StructuredData::ObjectSP json = StructuredData::ParseJSON(response);
+  StructuredData::Array *array = json->GetAsArray();
+  if (!array)
+    return make_parsing_error("JThreadsInfo: JSON array");
+
+  for (size_t i = 0; i < array->GetSize(); i++) {
+    StructuredData::Dictionary *thread_info;
+    array->GetItemAtIndexAsDictionary(i, thread_info);
+    if (!thread_info)
+      return make_parsing_error("JThreadsInfo: JSON obj at {0}", i);
+
+    StringRef name, reason;
+    thread_info->GetValueForKeyAsString("name", name);
+    thread_info->GetValueForKeyAsString("reason", reason);
+    uint64_t signal;
+    thread_info->GetValueForKeyAsInteger("signal", signal);
+    uint64_t tid;
+    thread_info->GetValueForKeyAsInteger("tid", tid);
+
+    StructuredData::Dictionary *register_dict;
+    thread_info->GetValueForKeyAsDictionary("registers", register_dict);
+    if (!register_dict)
+      return make_parsing_error("JThreadsInfo: registers JSON obj");
+
+    RegisterMap registers;
+
+    auto keys_obj = register_dict->GetKeys();
+    auto keys = keys_obj->GetAsArray();
+    for (size_t i = 0; i < keys->GetSize(); i++) {
+      StringRef key_str, value_str;
+      keys->GetItemAtIndexAsString(i, key_str);
+      register_dict->GetValueForKeyAsString(key_str, value_str);
+      unsigned int register_id;
+      if (key_str.getAsInteger(10, register_id))
+        return make_parsing_error("JThreadsInfo: register key[{0}]", i);
+
+      registers[register_id] = value_str.str();
+    }
+
+    jthreads_info.thread_infos[tid] =
+        ThreadInfo(name, reason, registers, signal);
+  }
+
+  return jthreads_info;
+}
+
+const ThreadInfoMap &JThreadsInfo::GetThreadInfos() const {
+  return thread_infos;
+}
+
+//====== StopReply =============================================================
+const U64Map &StopReply::GetThreadPcs() const { return thread_pcs; }
+
+Expected<StopReply> StopReply::Create(StringRef response,
+                                      llvm::support::endianness endian) {
+  StopReply stop_reply;
+
+  auto elements_or_error = SplitPairList("StopReply", response);
+  if (auto split_error = elements_or_error.takeError()) {
+    return std::move(split_error);
+  }
+
+  auto elements = *elements_or_error;
+  stop_reply.name = elements["name"];
+  stop_reply.reason = elements["reason"];
+
+  SmallVector<StringRef, 20> threads;
+  SmallVector<StringRef, 20> pcs;
+  elements["threads"].split(threads, ',');
+  elements["thread-pcs"].split(pcs, ',');
+  if (threads.size() != pcs.size())
+    return make_parsing_error("StopReply: thread/PC count mismatch");
+
+  for (size_t i = 0; i < threads.size(); i++) {
+    lldb::tid_t thread_id;
+    uint64_t pc;
+    if (threads[i].getAsInteger(16, thread_id))
+      return make_parsing_error("StopReply: thread ID at [{0}].", i);
+    if (pcs[i].getAsInteger(16, pc))
+      return make_parsing_error("StopReply: thread PC at [{0}].", i);
+
+    stop_reply.thread_pcs[thread_id] = pc;
+  }
+
+  for (auto i = elements.begin(); i != elements.end(); i++) {
+    StringRef key = i->getKey();
+    StringRef val = i->getValue();
+    if (key.size() >= 9 && key[0] == 'T' && key.substr(3, 6) == "thread") {
+      if (val.getAsInteger(16, stop_reply.thread))
+        return make_parsing_error("StopReply: thread id");
+      if (key.substr(1, 2).getAsInteger(16, stop_reply.signal))
+        return make_parsing_error("StopReply: stop signal");
+    } else if (key.size() == 2) {
+      unsigned int reg;
+      if (!key.getAsInteger(16, reg)) {
+        stop_reply.registers[reg] = val.str();
+      }
+    }
+  }
+
+  return stop_reply;
+}
+
+//====== Globals ===============================================================
+Expected<StringMap<StringRef>> SplitPairList(StringRef caller, StringRef str) {
+  SmallVector<StringRef, 20> elements;
+  str.split(elements, ';');
+
+  StringMap<StringRef> pairs;
+  for (StringRef s : elements) {
+    std::pair<StringRef, StringRef> pair = s.split(':');
+    if (pairs.count(pair.first))
+      return make_parsing_error("{0}: Duplicate Key: {1}", caller, pair.first);
+
+    pairs.insert(s.split(':'));
+  }
+
+  return pairs;
+}
+} // namespace llgs_tests
Index: unittests/tools/lldb-server/tests/TestClient.h
===================================================================
--- /dev/null
+++ unittests/tools/lldb-server/tests/TestClient.h
@@ -0,0 +1,61 @@
+//===-- TestClient.h --------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MessageObjects.h"
+#include "Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.h"
+#include "lldb/Core/ArchSpec.h"
+#include "lldb/Target/ProcessLaunchInfo.h"
+#include "llvm/ADT/Optional.h"
+#include <memory>
+#include <string>
+
+namespace llgs_tests {
+// TODO: Make the test client an abstract base class, with different children
+// for different types of connections: llgs v. debugserver
+class TestClient
+    : public lldb_private::process_gdb_remote::GDBRemoteCommunicationClient {
+public:
+  static void Initialize();
+  TestClient(const std::string &test_name, const std::string &test_case_name);
+  virtual ~TestClient();
+  LLVM_NODISCARD bool StartDebugger();
+  LLVM_NODISCARD bool StopDebugger();
+  LLVM_NODISCARD bool SetInferior(llvm::ArrayRef<std::string> inferior_args);
+  LLVM_NODISCARD bool ListThreadsInStopReply();
+  LLVM_NODISCARD bool SetBreakpoint(unsigned long address);
+  LLVM_NODISCARD bool ContinueAll();
+  LLVM_NODISCARD bool ContinueThread(unsigned long thread_id);
+  const ProcessInfo &GetProcessInfo();
+  llvm::Optional<JThreadsInfo> GetJThreadsInfo();
+  const StopReply &GetLatestStopReply();
+  LLVM_NODISCARD bool SendMessage(llvm::StringRef message);
+  LLVM_NODISCARD bool SendMessage(llvm::StringRef message,
+                                  std::string &response_string);
+  LLVM_NODISCARD bool SendMessage(llvm::StringRef message,
+                                  std::string &response_string,
+                                  PacketResult expected_result);
+  unsigned int GetPcRegisterId();
+
+private:
+  LLVM_NODISCARD bool Continue(llvm::StringRef message);
+  LLVM_NODISCARD bool GenerateConnectionAddress(std::string &address);
+  std::string GenerateLogFileName(const lldb_private::ArchSpec &arch) const;
+  std::string FormatFailedResult(
+      const std::string &message,
+      lldb_private::process_gdb_remote::GDBRemoteCommunication::PacketResult
+          result);
+
+  llvm::Optional<ProcessInfo> process_info;
+  llvm::Optional<StopReply> stop_reply;
+  lldb_private::ProcessLaunchInfo server_process_info;
+  std::string test_name;
+  std::string test_case_name;
+  unsigned int pc_register;
+};
+} // namespace llgs_tests
Index: unittests/tools/lldb-server/tests/TestClient.cpp
===================================================================
--- /dev/null
+++ unittests/tools/lldb-server/tests/TestClient.cpp
@@ -0,0 +1,276 @@
+//===-- TestClient.cpp ------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "TestClient.h"
+#include "lldb/Core/ArchSpec.h"
+#include "lldb/Host/HostInfo.h"
+#include "lldb/Host/common/TCPSocket.h"
+#include "lldb/Host/posix/ConnectionFileDescriptorPosix.h"
+#include "lldb/Host/posix/ProcessLauncherPosix.h"
+#include "lldb/Interpreter/Args.h"
+#include "lldb/Target/ProcessLaunchInfo.h"
+#include "llvm/ADT/StringExtras.h"
+#include "gtest/gtest.h"
+#include <cstdlib>
+#include <future>
+#include <sstream>
+#include <string>
+
+using namespace lldb;
+using namespace lldb_private;
+using namespace llvm;
+
+namespace llgs_tests {
+static const char g_local_host[] = "127.0.0.1";
+
+void TestClient::Initialize() { HostInfo::Initialize(); }
+
+TestClient::TestClient(const std::string &test_name,
+                       const std::string &test_case_name)
+    : test_name(test_name), test_case_name(test_case_name),
+      pc_register(UINT_MAX) {}
+
+TestClient::~TestClient() {}
+
+bool TestClient::StartDebugger() {
+  const ArchSpec &arch_spec = HostInfo::GetArchitecture();
+  Args args;
+  args.AppendArgument(LLDB_SERVER);
+  args.AppendArgument("gdbserver");
+  args.AppendArgument("--log-file=" + GenerateLogFileName(arch_spec));
+  args.AppendArgument("--log-channels=gdb-remote packets");
+  args.AppendArgument("--reverse-connect");
+  std::string connectionAddress;
+  if (!GenerateConnectionAddress(connectionAddress))
+    return false;
+
+  args.AppendArgument(connectionAddress);
+  server_process_info.SetArchitecture(arch_spec);
+  server_process_info.SetArguments(args, true);
+  Status status = Host::LaunchProcess(server_process_info);
+  if (status.Fail()) {
+    GTEST_LOG_(ERROR) << formatv("Failure to launch lldb server: {0}.", status)
+                             .str();
+    return false;
+  }
+
+  sleep(5);  // TODO: Sleep is bad. Can I wait for it to start?
+  SendAck(); // Send this as a handshake.
+  return true;
+}
+
+bool TestClient::StopDebugger() {
+  std::string response;
+  return SendMessage("k", response, PacketResult::ErrorDisconnected);
+}
+
+bool TestClient::SetInferior(llvm::ArrayRef<std::string> inferior_args) {
+  std::stringstream command;
+  command << "A";
+  for (size_t i = 0; i < inferior_args.size(); i++) {
+    if (i > 0)
+      command << ',';
+    std::string hex_encoded = toHex(inferior_args[i]);
+    command << hex_encoded.size() << ',' << i << ',' << hex_encoded;
+  }
+
+  if (!SendMessage(command.str()))
+    return false;
+  if (!SendMessage("qLaunchSuccess"))
+    return false;
+  std::string response;
+  if (!SendMessage("qProcessInfo", response))
+    return false;
+  auto create_or_error = ProcessInfo::Create(response);
+  if (auto create_error = create_or_error.takeError()) {
+    GTEST_LOG_(ERROR) << toString(std::move(create_error));
+    return false;
+  }
+
+  process_info = *create_or_error;
+  return true;
+}
+
+bool TestClient::ListThreadsInStopReply() {
+  return SendMessage("QListThreadsInStopReply");
+}
+
+bool TestClient::SetBreakpoint(unsigned long address) {
+  std::stringstream command;
+  command << "Z0," << std::hex << address << ",1";
+  return SendMessage(command.str());
+}
+
+bool TestClient::ContinueAll() { return Continue("vCont;c"); }
+
+bool TestClient::ContinueThread(unsigned long thread_id) {
+  return Continue(formatv("vCont;c:{0:x-}", thread_id).str());
+}
+
+const ProcessInfo &TestClient::GetProcessInfo() { return *process_info; }
+
+Optional<JThreadsInfo> TestClient::GetJThreadsInfo() {
+  std::string response;
+  if (!SendMessage("jThreadsInfo", response))
+    return llvm::None;
+  auto creation = JThreadsInfo::Create(response, process_info->GetEndian());
+  if (auto create_error = creation.takeError()) {
+    GTEST_LOG_(ERROR) << toString(std::move(create_error));
+    return llvm::None;
+  }
+
+  return std::move(*creation);
+}
+
+const StopReply &TestClient::GetLatestStopReply() {
+  return stop_reply.getValue();
+}
+
+bool TestClient::SendMessage(StringRef message) {
+  std::string dummy_string;
+  return SendMessage(message, dummy_string);
+}
+
+bool TestClient::SendMessage(StringRef message, std::string &response_string) {
+  if (!SendMessage(message, response_string, PacketResult::Success))
+    return false;
+  else if (response_string[0] == 'E') {
+    GTEST_LOG_(ERROR) << "Error " << response_string
+                      << " while sending message: " << message.str();
+    return false;
+  }
+
+  return true;
+}
+
+bool TestClient::SendMessage(StringRef message, std::string &response_string,
+                             PacketResult expected_result) {
+  StringExtractorGDBRemote response;
+  GTEST_LOG_(INFO) << "Send Packet: " << message.str();
+  PacketResult result = SendPacketAndWaitForResponse(message, response, false);
+  response.GetEscapedBinaryData(response_string);
+  GTEST_LOG_(INFO) << "Read Packet: " << response_string;
+  if (result != expected_result) {
+    GTEST_LOG_(ERROR) << FormatFailedResult(message, result);
+    return false;
+  }
+
+  return true;
+}
+
+unsigned int TestClient::GetPcRegisterId() {
+  if (pc_register != UINT_MAX)
+    return pc_register;
+
+  for (unsigned int register_id = 0;; register_id++) {
+    std::string message = formatv("qRegisterInfo{0:x-}", register_id).str();
+    std::string response;
+    if (!SendMessage(message, response)) {
+      GTEST_LOG_(ERROR) << "Unable to query register ID for PC register.";
+      return UINT_MAX;
+    }
+
+    auto elements_or_error = SplitPairList("GetPcRegisterId", response);
+    if (auto split_error = elements_or_error.takeError()) {
+      GTEST_LOG_(ERROR) << "GetPcRegisterId: Error splitting response: "
+                        << response;
+      return UINT_MAX;
+    }
+
+    auto elements = *elements_or_error;
+    if (elements["alt-name"] == "pc" || elements["generic"] == "pc") {
+      pc_register = register_id;
+      break;
+    }
+  }
+
+  return pc_register;
+}
+
+bool TestClient::Continue(StringRef message) {
+  if (!process_info.hasValue()) {
+    GTEST_LOG_(ERROR) << "Continue() called before process_info initialized.";
+    return false;
+  }
+
+  std::string response;
+  if (!SendMessage(message, response))
+    return false;
+  auto creation = StopReply::Create(response, process_info->GetEndian());
+  if (auto create_error = creation.takeError()) {
+    GTEST_LOG_(ERROR) << toString(std::move(create_error));
+    return false;
+  }
+
+  stop_reply = std::move(*creation);
+  return true;
+}
+
+bool TestClient::GenerateConnectionAddress(std::string &address) {
+  StartListenThread(g_local_host, 0);
+  auto connection = static_cast<ConnectionFileDescriptor *>(GetConnection());
+  uint16_t listening_port = connection->GetListeningPort(UINT32_MAX);
+  if (listening_port <= 0) {
+    GTEST_LOG_(ERROR) << "GetListeningPort failed.";
+    return false;
+  }
+
+  raw_string_ostream address_stream(address);
+  address_stream << g_local_host << ":" << listening_port;
+  address_stream.str();
+  return true;
+}
+
+std::string TestClient::GenerateLogFileName(const ArchSpec &arch) const {
+  std::string log_file_name;
+  raw_string_ostream log_file(log_file_name);
+  log_file << "lldb-test-traces/lldb-" << test_case_name << '-' << test_name
+           << '-' << arch.GetArchitectureName() << ".log";
+  return log_file.str();
+}
+
+std::string TestClient::FormatFailedResult(const std::string &message,
+                                           PacketResult result) {
+  std::string formatted_error;
+  raw_string_ostream error_stream(formatted_error);
+  error_stream << "Failure sending message: " << message << " Result: ";
+
+  switch (result) {
+  case PacketResult::ErrorSendFailed:
+    error_stream << "ErrorSendFailed";
+    break;
+  case PacketResult::ErrorSendAck:
+    error_stream << "ErrorSendAck";
+    break;
+  case PacketResult::ErrorReplyFailed:
+    error_stream << "ErrorReplyFailed";
+    break;
+  case PacketResult::ErrorReplyTimeout:
+    error_stream << "ErrorReplyTimeout";
+    break;
+  case PacketResult::ErrorReplyInvalid:
+    error_stream << "ErrorReplyInvalid";
+    break;
+  case PacketResult::ErrorReplyAck:
+    error_stream << "ErrorReplyAck";
+    break;
+  case PacketResult::ErrorDisconnected:
+    error_stream << "ErrorDisconnected";
+    break;
+  case PacketResult::ErrorNoSequenceLock:
+    error_stream << "ErrorNoSequenceLock";
+    break;
+  default:
+    error_stream << "Unknown Error";
+  }
+
+  error_stream.str();
+  return formatted_error;
+}
+} // namespace llgs_tests
Index: unittests/tools/lldb-server/tests/ThreadIdsInJstopinfoTest.cpp
===================================================================
--- /dev/null
+++ unittests/tools/lldb-server/tests/ThreadIdsInJstopinfoTest.cpp
@@ -0,0 +1,58 @@
+//===-- ThreadsInJstopinfoTest.cpp ------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "TestClient.h"
+#include "gtest/gtest.h"
+#include <string>
+
+using namespace llgs_tests;
+
+class ThreadsInJstopinfoTest : public ::testing::Test {
+protected:
+  virtual void SetUp() { TestClient::Initialize(); }
+};
+
+TEST_F(ThreadsInJstopinfoTest, TestStopReplyContainsThreadPcsLlgs) {
+  std::vector<std::string> inferior_args;
+  // This inferior spawns N threads, then forces a break.
+  inferior_args.push_back(THREAD_INFERIOR);
+  inferior_args.push_back("4");
+
+  auto test_info = ::testing::UnitTest::GetInstance()->current_test_info();
+
+  TestClient client(test_info->name(), test_info->test_case_name());
+  ASSERT_TRUE(client.StartDebugger());
+  ASSERT_TRUE(client.SetInferior(inferior_args));
+  ASSERT_TRUE(client.ListThreadsInStopReply());
+  ASSERT_TRUE(client.ContinueAll());
+  unsigned int pc_reg = client.GetPcRegisterId();
+  ASSERT_NE(pc_reg, UINT_MAX);
+
+  auto jthreads_info = client.GetJThreadsInfo();
+  ASSERT_TRUE(jthreads_info);
+
+  auto stop_reply = client.GetLatestStopReply();
+  auto stop_reply_pcs = stop_reply.GetThreadPcs();
+  auto thread_infos = jthreads_info->GetThreadInfos();
+  ASSERT_EQ(stop_reply_pcs.size(), thread_infos.size())
+      << "Thread count mismatch.";
+
+  for (auto stop_reply_pc : stop_reply_pcs) {
+    unsigned long tid = stop_reply_pc.first;
+    ASSERT_TRUE(thread_infos.find(tid) != thread_infos.end())
+        << "Thread ID: " << tid << " not in JThreadsInfo.";
+    uint64_t pc_value;
+    ASSERT_TRUE(thread_infos[tid].ReadRegisterAsUint64(pc_reg, pc_value))
+        << "Failure reading ThreadInfo register " << pc_reg;
+    ASSERT_EQ(stop_reply_pcs[tid], pc_value)
+        << "Mismatched PC for thread: " << tid;
+  }
+
+  ASSERT_TRUE(client.StopDebugger());
+}