Index: lldb/trunk/unittests/Utility/CMakeLists.txt
===================================================================
--- lldb/trunk/unittests/Utility/CMakeLists.txt
+++ lldb/trunk/unittests/Utility/CMakeLists.txt
@@ -1,5 +1,8 @@
 add_lldb_unittest(UtilityTests
+  ModuleCacheTest.cpp
   StringExtractorTest.cpp
   TaskPoolTest.cpp
   UriParserTest.cpp
   )
+
+add_unittest_inputs(UtilityTests TestModule.so)
Index: lldb/trunk/unittests/Utility/Inputs/TestModule.c
===================================================================
--- lldb/trunk/unittests/Utility/Inputs/TestModule.c
+++ lldb/trunk/unittests/Utility/Inputs/TestModule.c
@@ -0,0 +1,10 @@
+// Compile with $CC -nostdlib -shared TestModule.c -o TestModule.so
+// The actual contents of the test module is not important here. I am using this because it
+// produces an extremely tiny (but still perfectly valid) module.
+
+void
+boom(void)
+{
+    char *BOOM;
+    *BOOM = 47;
+}
Index: lldb/trunk/unittests/Utility/ModuleCacheTest.cpp
===================================================================
--- lldb/trunk/unittests/Utility/ModuleCacheTest.cpp
+++ lldb/trunk/unittests/Utility/ModuleCacheTest.cpp
@@ -0,0 +1,179 @@
+#include "gtest/gtest.h"
+
+#include "llvm/ADT/SmallString.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Path.h"
+
+#include "Plugins/ObjectFile/ELF/ObjectFileELF.h"
+#include "Utility/ModuleCache.h"
+#include "lldb/Core/Module.h"
+#include "lldb/Core/ModuleSpec.h"
+#include "lldb/Host/HostInfo.h"
+#include "lldb/Symbol/SymbolContext.h"
+
+extern const char *TestMainArgv0;
+
+using namespace lldb_private;
+using namespace lldb;
+
+namespace
+{
+
+class ModuleCacheTest : public testing::Test
+{
+public:
+    static void
+    SetUpTestCase();
+
+    static void
+    TearDownTestCase();
+
+protected:
+    static FileSpec s_cache_dir;
+    static llvm::SmallString<128> s_test_executable;
+
+    void
+    TryGetAndPut(const FileSpec &cache_dir, const char *hostname, bool expect_download);
+};
+}
+
+FileSpec ModuleCacheTest::s_cache_dir;
+llvm::SmallString<128> ModuleCacheTest::s_test_executable;
+
+static const char dummy_hostname[] = "dummy_hostname";
+static const char dummy_remote_dir[] = "bin";
+static const char module_name[] = "TestModule.so";
+static const char module_uuid[] = "F4E7E991-9B61-6AD4-0073-561AC3D9FA10-C043A476";
+static const uint32_t uuid_bytes = 20;
+static const size_t module_size = 5602;
+
+static FileSpec
+GetDummyRemotePath()
+{
+    FileSpec fs("/", false, FileSpec::ePathSyntaxPosix);
+    fs.AppendPathComponent(dummy_remote_dir);
+    fs.AppendPathComponent(module_name);
+    return fs;
+}
+
+static FileSpec
+GetUuidView(FileSpec spec)
+{
+    spec.AppendPathComponent(".cache");
+    spec.AppendPathComponent(module_uuid);
+    spec.AppendPathComponent(module_name);
+    return spec;
+}
+
+static FileSpec
+GetSysrootView(FileSpec spec, const char *hostname)
+{
+    spec.AppendPathComponent(hostname);
+    spec.AppendPathComponent(dummy_remote_dir);
+    spec.AppendPathComponent(module_name);
+    return spec;
+}
+
+void
+ModuleCacheTest::SetUpTestCase()
+{
+    HostInfo::Initialize();
+    ObjectFileELF::Initialize();
+
+    FileSpec tmpdir_spec;
+    HostInfo::GetLLDBPath(lldb::ePathTypeLLDBTempSystemDir, s_cache_dir);
+
+    llvm::StringRef exe_folder = llvm::sys::path::parent_path(TestMainArgv0);
+    s_test_executable = exe_folder;
+    llvm::sys::path::append(s_test_executable, "Inputs", module_name);
+}
+
+void
+ModuleCacheTest::TearDownTestCase()
+{
+    ObjectFileELF::Terminate();
+    HostInfo::Terminate();
+}
+
+static void
+VerifyDiskState(const FileSpec &cache_dir, const char *hostname)
+{
+    FileSpec uuid_view = GetUuidView(cache_dir);
+    EXPECT_TRUE(uuid_view.Exists()) << "uuid_view is: " << uuid_view.GetCString();
+    EXPECT_EQ(module_size, uuid_view.GetByteSize());
+
+    FileSpec sysroot_view = GetSysrootView(cache_dir, hostname);
+    EXPECT_TRUE(sysroot_view.Exists()) << "sysroot_view is: " << sysroot_view.GetCString();
+    EXPECT_EQ(module_size, sysroot_view.GetByteSize());
+}
+
+void
+ModuleCacheTest::TryGetAndPut(const FileSpec &cache_dir, const char *hostname, bool expect_download)
+{
+    ModuleCache mc;
+    ModuleSpec module_spec;
+    module_spec.GetFileSpec() = GetDummyRemotePath();
+    module_spec.GetUUID().SetFromCString(module_uuid, uuid_bytes);
+    module_spec.SetObjectSize(module_size);
+    ModuleSP module_sp;
+    bool did_create;
+    bool download_called = false;
+
+    Error error = mc.GetAndPut(
+        cache_dir, hostname, module_spec,
+        [this, &download_called](const ModuleSpec &module_spec, const FileSpec &tmp_download_file_spec) {
+            download_called = true;
+            EXPECT_STREQ(GetDummyRemotePath().GetCString(), module_spec.GetFileSpec().GetCString());
+            std::error_code ec = llvm::sys::fs::copy_file(s_test_executable, tmp_download_file_spec.GetCString());
+            EXPECT_FALSE(ec);
+            return Error();
+        },
+        [](const ModuleSP &module_sp, const FileSpec &tmp_download_file_spec) { return Error("Not supported."); },
+        module_sp, &did_create);
+    EXPECT_EQ(expect_download, download_called);
+
+    EXPECT_TRUE(error.Success()) << "Error was: " << error.AsCString();
+    EXPECT_TRUE(did_create);
+    ASSERT_TRUE(bool(module_sp));
+
+    SymbolContextList sc_list;
+    EXPECT_EQ(1u, module_sp->FindFunctionSymbols(ConstString("boom"), eFunctionNameTypeFull, sc_list));
+    EXPECT_STREQ(GetDummyRemotePath().GetCString(), module_sp->GetPlatformFileSpec().GetCString());
+    EXPECT_STREQ(module_uuid, module_sp->GetUUID().GetAsString().c_str());
+}
+
+TEST_F(ModuleCacheTest, GetAndPut)
+{
+    FileSpec test_cache_dir = s_cache_dir;
+    test_cache_dir.AppendPathComponent("GetAndPut");
+
+    const bool expect_download = true;
+    TryGetAndPut(test_cache_dir, dummy_hostname, expect_download);
+    VerifyDiskState(test_cache_dir, dummy_hostname);
+}
+
+TEST_F(ModuleCacheTest, GetAndPutUuidExists)
+{
+    FileSpec test_cache_dir = s_cache_dir;
+    test_cache_dir.AppendPathComponent("GetAndPutUuidExists");
+
+    FileSpec uuid_view = GetUuidView(test_cache_dir);
+    std::error_code ec = llvm::sys::fs::create_directories(uuid_view.GetDirectory().GetCString());
+    ASSERT_FALSE(ec);
+    ec = llvm::sys::fs::copy_file(s_test_executable, uuid_view.GetCString());
+    ASSERT_FALSE(ec);
+
+    const bool expect_download = false;
+    TryGetAndPut(test_cache_dir, dummy_hostname, expect_download);
+    VerifyDiskState(test_cache_dir, dummy_hostname);
+}
+
+TEST_F(ModuleCacheTest, GetAndPutStrangeHostname)
+{
+    FileSpec test_cache_dir = s_cache_dir;
+    test_cache_dir.AppendPathComponent("GetAndPutStrangeHostname");
+
+    const bool expect_download = true;
+    TryGetAndPut(test_cache_dir, "tab\tcolon:asterisk*", expect_download);
+    VerifyDiskState(test_cache_dir, "tab_colon_asterisk_");
+}