Index: unittests/Host/CMakeLists.txt
===================================================================
--- unittests/Host/CMakeLists.txt
+++ unittests/Host/CMakeLists.txt
@@ -3,6 +3,7 @@
   HostInfoTest.cpp
   HostTest.cpp
   MainLoopTest.cpp
+  NativeProcessProtocolTest.cpp
   SocketAddressTest.cpp
   SocketTest.cpp
   SymbolsTest.cpp
@@ -22,4 +23,5 @@
     lldbCore
     lldbHost
     lldbUtilityHelpers
+    LLVMTestingSupport
   )
Index: unittests/Host/NativeProcessProtocolTest.cpp
===================================================================
--- unittests/Host/NativeProcessProtocolTest.cpp
+++ unittests/Host/NativeProcessProtocolTest.cpp
@@ -0,0 +1,154 @@
+//===-- NativeProcessProtocolTest.cpp ---------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Host/common/NativeProcessProtocol.h"
+#include "llvm/Testing/Support/Error.h"
+#include "gmock/gmock.h"
+
+using namespace lldb_private;
+using namespace lldb;
+using namespace testing;
+
+namespace {
+class MockDelegate : public NativeProcessProtocol::NativeDelegate {
+public:
+  MOCK_METHOD1(InitializeDelegate, void(NativeProcessProtocol *Process));
+  MOCK_METHOD2(ProcessStateChanged,
+               void(NativeProcessProtocol *Process, StateType State));
+  MOCK_METHOD1(DidExec, void(NativeProcessProtocol *Process));
+};
+
+class MockProcess : public NativeProcessProtocol {
+public:
+  MockProcess(NativeDelegate &Delegate, const ArchSpec &Arch,
+              lldb::pid_t Pid = 1)
+      : NativeProcessProtocol(Pid, -1, Delegate), Arch(Arch) {}
+
+  MOCK_METHOD1(Resume, Status(const ResumeActionList &ResumeActions));
+  MOCK_METHOD0(Halt, Status());
+  MOCK_METHOD0(Detach, Status());
+  MOCK_METHOD1(Signal, Status(int Signo));
+  MOCK_METHOD0(Kill, Status());
+  MOCK_METHOD3(AllocateMemory,
+               Status(size_t Size, uint32_t Permissions, addr_t &Addr));
+  MOCK_METHOD1(DeallocateMemory, Status(addr_t Addr));
+  MOCK_METHOD0(GetSharedLibraryInfoAddress, addr_t());
+  MOCK_METHOD0(UpdateThreads, size_t());
+  MOCK_CONST_METHOD0(GetAuxvData,
+                     llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>());
+  MOCK_METHOD2(GetLoadedModuleFileSpec,
+               Status(const char *ModulePath, FileSpec &Spec));
+  MOCK_METHOD2(GetFileLoadAddress,
+               Status(const llvm::StringRef &FileName, addr_t &Addr));
+
+  const ArchSpec &GetArchitecture() const override { return Arch; }
+  Status SetBreakpoint(lldb::addr_t Addr, uint32_t Size,
+                       bool Hardware) override {
+    if (Hardware)
+      return SetHardwareBreakpoint(Addr, Size);
+    else
+      return SetSoftwareBreakpoint(Addr, Size);
+  }
+
+  // Redirect base class Read/Write Memory methods to functions whose signatures
+  // are more mock-friendly.
+  Status ReadMemory(addr_t Addr, void *Buf, size_t Size,
+                    size_t &BytesRead) override;
+  Status WriteMemory(addr_t Addr, const void *Buf, size_t Size,
+                     size_t &BytesWritten) override;
+
+  MOCK_METHOD2(ReadMemory,
+               llvm::Expected<std::vector<uint8_t>>(addr_t Addr, size_t Size));
+  MOCK_METHOD2(WriteMemory,
+               llvm::Expected<size_t>(addr_t Addr,
+                                      llvm::ArrayRef<uint8_t> Data));
+
+  using NativeProcessProtocol::GetSoftwareBreakpointTrapOpcode;
+
+private:
+  ArchSpec Arch;
+};
+} // namespace
+
+Status MockProcess::ReadMemory(addr_t Addr, void *Buf, size_t Size,
+                               size_t &BytesRead) {
+  auto ExpectedMemory = ReadMemory(Addr, Size);
+  if (!ExpectedMemory) {
+    BytesRead = 0;
+    return Status(ExpectedMemory.takeError());
+  }
+  BytesRead = ExpectedMemory->size();
+  assert(BytesRead <= Size);
+  std::memcpy(Buf, ExpectedMemory->data(), BytesRead);
+  return Status();
+}
+
+Status MockProcess::WriteMemory(addr_t Addr, const void *Buf, size_t Size,
+                                size_t &BytesWritten) {
+  auto ExpectedBytes = WriteMemory(
+      Addr, llvm::makeArrayRef(static_cast<const uint8_t *>(Buf), Size));
+  if (!ExpectedBytes) {
+    BytesWritten = 0;
+    return Status(ExpectedBytes.takeError());
+  }
+  BytesWritten = *ExpectedBytes;
+  return Status();
+}
+
+TEST(NativeProcessProtocolTest, SetBreakpoint) {
+  NiceMock<MockDelegate> DummyDelegate;
+  MockProcess Process(DummyDelegate, ArchSpec("x86_64-pc-linux"));
+  auto Trap = cantFail(Process.GetSoftwareBreakpointTrapOpcode(1));
+  InSequence S;
+  EXPECT_CALL(Process, ReadMemory(0x47, 1))
+      .WillOnce(Return(ByMove(std::vector<uint8_t>{0xbb})));
+  EXPECT_CALL(Process, WriteMemory(0x47, Trap)).WillOnce(Return(ByMove(1)));
+  EXPECT_CALL(Process, ReadMemory(0x47, 1)).WillOnce(Return(ByMove(Trap)));
+  EXPECT_THAT_ERROR(Process.SetBreakpoint(0x47, 0, false).ToError(),
+                    llvm::Succeeded());
+}
+
+TEST(NativeProcessProtocolTest, SetBreakpointFailRead) {
+  NiceMock<MockDelegate> DummyDelegate;
+  MockProcess Process(DummyDelegate, ArchSpec("x86_64-pc-linux"));
+  EXPECT_CALL(Process, ReadMemory(0x47, 1))
+      .WillOnce(Return(ByMove(
+          llvm::createStringError(llvm::inconvertibleErrorCode(), "Foo"))));
+  EXPECT_THAT_ERROR(Process.SetBreakpoint(0x47, 0, false).ToError(),
+                    llvm::Failed());
+}
+
+TEST(NativeProcessProtocolTest, SetBreakpointFailWrite) {
+  NiceMock<MockDelegate> DummyDelegate;
+  MockProcess Process(DummyDelegate, ArchSpec("x86_64-pc-linux"));
+  auto Trap = cantFail(Process.GetSoftwareBreakpointTrapOpcode(1));
+  InSequence S;
+  EXPECT_CALL(Process, ReadMemory(0x47, 1))
+      .WillOnce(Return(ByMove(std::vector<uint8_t>{0xbb})));
+  EXPECT_CALL(Process, WriteMemory(0x47, Trap))
+      .WillOnce(Return(ByMove(
+          llvm::createStringError(llvm::inconvertibleErrorCode(), "Foo"))));
+  EXPECT_THAT_ERROR(Process.SetBreakpoint(0x47, 0, false).ToError(),
+                    llvm::Failed());
+}
+
+TEST(NativeProcessProtocolTest, SetBreakpointFailVerify) {
+  NiceMock<MockDelegate> DummyDelegate;
+  MockProcess Process(DummyDelegate, ArchSpec("x86_64-pc-linux"));
+  auto Trap = cantFail(Process.GetSoftwareBreakpointTrapOpcode(1));
+  InSequence S;
+  EXPECT_CALL(Process, ReadMemory(0x47, 1))
+      .WillOnce(Return(ByMove(std::vector<uint8_t>{0xbb})));
+  EXPECT_CALL(Process, WriteMemory(0x47, Trap)).WillOnce(Return(ByMove(1)));
+  EXPECT_CALL(Process, ReadMemory(0x47, 1))
+      .WillOnce(Return(ByMove(
+          llvm::createStringError(llvm::inconvertibleErrorCode(), "Foo"))));
+  EXPECT_THAT_ERROR(Process.SetBreakpoint(0x47, 0, false).ToError(),
+                    llvm::Failed());
+}