diff --git a/BUILD.gn b/BUILD.gn
index 80864d9a332b25a05a58f1e6f430234c00a798de..a1f6008b9095c1595b06124d16ead3deda6934f2 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1,4 +1,4 @@
-# Copyright (c) 2022 Huawei Device Co., Ltd.
+# Copyright (c) 2022-2023 Huawei Device Co., Ltd.
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
@@ -44,5 +44,6 @@ group("test_target") {
     "test/resource/bmssystemtestability/abilitySrc:bms_system_test_app",
     "test/sceneProject:test_hap",
     "test/systemtest/common/bms:systemtest_bms",
+    "test/unittest/bundle_mgr_client_test:unittest",
   ]
 }
diff --git a/test/unittest/bundle_mgr_client_test/BUILD.gn b/test/unittest/bundle_mgr_client_test/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..4a38a964d617706c7a13a482fc3abdd4a2527bd8
--- /dev/null
+++ b/test/unittest/bundle_mgr_client_test/BUILD.gn
@@ -0,0 +1,47 @@
+# Copyright (c) 2023 Huawei Device Co., Ltd.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import("//build/test.gni")
+import("../../../appexecfwk.gni")
+
+module_output_path = "bundle_framework/common"
+
+ohos_unittest("BundleMgrClientTest") {
+  module_out_path = module_output_path
+
+  sources = [ "bundle_mgr_client_test.cpp" ]
+
+  configs = [
+    "${common_path}:appexecfwk_common_config",
+    "${common_path}/test:common_test_config",
+  ]
+
+  deps = [
+    "${base_path}:appexecfwk_base",
+    "${core_path}:appexecfwk_core",
+    "//third_party/googletest:gtest_main",
+  ]
+
+  external_deps = [
+    "ability_base:want",
+    "c_utils:utils",
+    "hilog:libhilog",
+    "ipc:ipc_core",
+  ]
+}
+
+group("unittest") {
+  testonly = true
+
+  deps = [ ":BundleMgrClientTest" ]
+}
diff --git a/test/unittest/bundle_mgr_client_test/bundle_mgr_client_test.cpp b/test/unittest/bundle_mgr_client_test/bundle_mgr_client_test.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..f3f00f85198cd4acedf2fbde90550ce3ffd1decc
--- /dev/null
+++ b/test/unittest/bundle_mgr_client_test/bundle_mgr_client_test.cpp
@@ -0,0 +1,542 @@
+/*
+ * Copyright (c) 2023 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <gtest/gtest.h>
+
+#define private public
+#include "bundle_mgr_client.h"
+#include "bundle_mgr_client_impl.h"
+#undef private
+
+using namespace testing;
+using namespace testing::ext;
+
+namespace OHOS {
+namespace AppExecFwk {
+class BundleMgrClientTest : public testing::Test {
+public:
+    static void SetUpTestCase();
+    static void TearDownTestCase();
+    void SetUp() override;
+    void TearDown() override;
+};
+
+void BundleMgrClientTest::SetUpTestCase(void)
+{}
+
+void BundleMgrClientTest::TearDownTestCase(void)
+{}
+
+void BundleMgrClientTest::SetUp()
+{}
+
+void BundleMgrClientTest::TearDown()
+{}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetBundleInfo_001
+ * @tc.desc: GetBundleInfo
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetBundleInfo_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string bundleName = "ohos.global.systemres";
+    int32_t flags = 0;
+    BundleInfo bundleInfo;
+    int32_t userId = 100;
+    auto ret = client.GetBundleInfo(bundleName, flags, bundleInfo, userId);
+    EXPECT_EQ(ret, true);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetHapModuleInfo_001
+ * @tc.desc: GetHapModuleInfo
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetHapModuleInfo_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    AbilityInfo abilityInfo;
+    HapModuleInfo hapModuleInfo;
+    auto ret = client.GetHapModuleInfo(abilityInfo, hapModuleInfo);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetAbilityLabel_001
+ * @tc.desc: GetAbilityLabel
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetAbilityLabel_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string bundleName;
+    std::string abilityName;
+    auto ret = client.GetAbilityLabel(bundleName, abilityName);
+    EXPECT_EQ(ret, "");
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetAppType_001
+ * @tc.desc: GetAppType
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetAppType_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string bundleName;
+    auto ret = client.GetAppType(bundleName);
+    EXPECT_EQ(ret, "");
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetBaseSharedBundleInfos_001
+ * @tc.desc: GetBaseSharedBundleInfos
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetBaseSharedBundleInfos_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string bundleName;
+    std::vector<BaseSharedBundleInfo> baseSharedBundleInfos;
+    auto ret = client.GetBaseSharedBundleInfos(bundleName, baseSharedBundleInfos);
+    EXPECT_NE(ret, ERR_OK);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetBundleInfoForSelf_001
+ * @tc.desc: GetBundleInfoForSelf
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetBundleInfoForSelf_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    int32_t flags = 0;
+    BundleInfo bundleInfo;
+    auto ret = client.GetBundleInfoForSelf(flags, bundleInfo);
+    EXPECT_NE(ret, ERR_OK);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetDependentBundleInfo_001
+ * @tc.desc: GetDependentBundleInfo
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetDependentBundleInfo_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string sharedBundleName;
+    BundleInfo sharedBundleInfo;
+    auto ret = client.GetDependentBundleInfo(sharedBundleName, sharedBundleInfo);
+    EXPECT_NE(ret, ERR_OK);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetGroupDir_001
+ * @tc.desc: GetGroupDir
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetGroupDir_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string dataGroupId;
+    std::string dir;
+    auto ret = client.GetGroupDir(dataGroupId, dir);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetOverlayManagerProxy_001
+ * @tc.desc: GetOverlayManagerProxy
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetOverlayManagerProxy_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    auto ret = client.GetOverlayManagerProxy();
+    EXPECT_NE(ret, nullptr);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_QueryAbilityInfo_002
+ * @tc.desc: QueryAbilityInfo
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_QueryAbilityInfo_002, TestSize.Level1)
+{
+    BundleMgrClient client;
+    Want want;
+    AbilityInfo abilityInfo;
+    auto ret = client.QueryAbilityInfo(want, abilityInfo);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_QueryAbilityInfo_001
+ * @tc.desc: QueryAbilityInfo
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_QueryAbilityInfo_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    Want want;
+    int32_t flags = 0;
+    int32_t userId = 100;
+    AbilityInfo abilityInfo;
+    const sptr<IRemoteObject> callBack = nullptr;
+    auto ret = client.QueryAbilityInfo(want, flags, userId, abilityInfo, callBack);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetBundleInfos_001
+ * @tc.desc: GetBundleInfos
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetBundleInfos_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    BundleFlag flag = BundleFlag::GET_BUNDLE_WITH_ABILITIES;
+    std::vector<BundleInfo> bundleInfos;
+    int32_t userId = 100;
+    auto ret = client.GetBundleInfos(flag, bundleInfos, userId);
+    EXPECT_EQ(ret, true);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_ImplicitQueryInfos_001
+ * @tc.desc: ImplicitQueryInfos
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_ImplicitQueryInfos_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    Want want;
+    int32_t flags = 0;
+    int32_t userId = 100;
+    bool withDefault = false;
+    std::vector<AbilityInfo> abilityInfos;
+    std::vector<ExtensionAbilityInfo> extensionInfos;
+    auto ret = client.ImplicitQueryInfos(want, flags, userId, withDefault, abilityInfos, extensionInfos);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_CleanBundleDataFiles_001
+ * @tc.desc: CleanBundleDataFiles
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_CleanBundleDataFiles_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string bundleName;
+    int32_t userId = 100;
+    auto ret = client.CleanBundleDataFiles(bundleName, userId);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_QueryDataGroupInfos_001
+ * @tc.desc: QueryDataGroupInfos
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_QueryDataGroupInfos_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string bundleName;
+    int32_t userId = 100;
+    std::vector<DataGroupInfo> infos;
+    auto ret = client.QueryDataGroupInfos(bundleName, userId, infos);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetBundleGidsByUid_001
+ * @tc.desc: GetBundleGidsByUid
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetBundleGidsByUid_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string bundleName;
+    int32_t uid = 100;
+    std::vector<int> gids;
+    auto ret = client.GetBundleGidsByUid(bundleName, uid, gids);
+    EXPECT_EQ(ret, true);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_RegisterBundleEventCallback_001
+ * @tc.desc: RegisterBundleEventCallback
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_RegisterBundleEventCallback_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    const sptr<IBundleEventCallback> bundleEventCallback = nullptr;
+    auto ret = client.RegisterBundleEventCallback(bundleEventCallback);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetQuickFixManagerProxy_001
+ * @tc.desc: GetQuickFixManagerProxy
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetQuickFixManagerProxy_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    auto ret = client.GetQuickFixManagerProxy();
+    EXPECT_NE(ret, nullptr);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_QueryExtensionAbilityInfos_002
+ * @tc.desc: QueryExtensionAbilityInfos
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_QueryExtensionAbilityInfos_002, TestSize.Level1)
+{
+    BundleMgrClient client;
+    Want want;
+    ExtensionAbilityType extensionType = ExtensionAbilityType::ACCESSIBILITY;
+    int32_t flag = 0;
+    int32_t userId = 100;
+    std::vector<ExtensionAbilityInfo> extensionInfos;
+    auto ret = client.QueryExtensionAbilityInfos(want, extensionType, flag, userId, extensionInfos);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetAppControlProxy_001
+ * @tc.desc: GetAppControlProxy
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetAppControlProxy_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    auto ret = client.GetAppControlProxy();
+    EXPECT_NE(ret, nullptr);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_QueryExtensionAbilityInfos_001
+ * @tc.desc: QueryExtensionAbilityInfos
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_QueryExtensionAbilityInfos_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    Want want;
+    int32_t flag = 0;
+    int32_t userId = 100;
+    std::vector<ExtensionAbilityInfo> extensionInfos;
+    auto ret = client.QueryExtensionAbilityInfos(want, flag, userId, extensionInfos);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetApplicationInfo_001
+ * @tc.desc: GetApplicationInfo
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetApplicationInfo_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string appName;
+    ApplicationFlag flag = ApplicationFlag::GET_ALL_APPLICATION_INFO;
+    int userId = 100;
+    ApplicationInfo appInfo;
+    auto ret = client.GetApplicationInfo(appName, flag, userId, appInfo);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_UnregisterBundleEventCallback_001
+ * @tc.desc: UnregisterBundleEventCallback
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_UnregisterBundleEventCallback_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    sptr<IBundleEventCallback> bundleEventCallback = nullptr;
+    auto ret = client.UnregisterBundleEventCallback(bundleEventCallback);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_QueryExtensionAbilityInfoByUri_001
+ * @tc.desc: QueryExtensionAbilityInfoByUri
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_QueryExtensionAbilityInfoByUri_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string uri;
+    int32_t userId = 100;
+    ExtensionAbilityInfo extensionAbilityInfo;
+    auto ret = client.QueryExtensionAbilityInfoByUri(uri, userId, extensionAbilityInfo);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_QueryAbilityInfoByUri_001
+ * @tc.desc: QueryAbilityInfoByUri
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_QueryAbilityInfoByUri_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string abilityUri;
+    int32_t userId = 100;
+    AbilityInfo abilityInfo;
+    auto ret = client.QueryAbilityInfoByUri(abilityUri, userId, abilityInfo);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_ImplicitQueryInfoByPriority_001
+ * @tc.desc: ImplicitQueryInfoByPriority
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_ImplicitQueryInfoByPriority_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    Want want;
+    int32_t flags = 0;
+    int32_t userId = 100;
+    AbilityInfo abilityInfo;
+    ExtensionAbilityInfo extensionInfo;
+    auto ret = client.ImplicitQueryInfoByPriority(want, flags, userId, abilityInfo, extensionInfo);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetBundleInfos_002
+ * @tc.desc: GetBundleInfos
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetBundleInfos_002, TestSize.Level1)
+{
+    BundleMgrClient client;
+    int32_t flags = 0;
+    std::vector<BundleInfo> bundleInfos;
+    int32_t userId = 100;
+    auto ret = client.GetBundleInfos(flags, bundleInfos, userId);
+    EXPECT_EQ(ret, true);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetHapModuleInfo_002
+ * @tc.desc: GetHapModuleInfo
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetHapModuleInfo_002, TestSize.Level1)
+{
+    BundleMgrClient client;
+    AbilityInfo abilityInfo;
+    int32_t userId = 100;
+    HapModuleInfo hapModuleInfo;
+    auto ret = client.GetHapModuleInfo(abilityInfo, userId, hapModuleInfo);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetUidByBundleName_001
+ * @tc.desc: GetUidByBundleName
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetUidByBundleName_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string bundleName;
+    int32_t userId = 100;
+    auto ret = client.GetUidByBundleName(bundleName, userId);
+    EXPECT_EQ(ret, Constants::INVALID_UID);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetApplicationInfo_002
+ * @tc.desc: GetApplicationInfo
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetApplicationInfo_002, TestSize.Level1)
+{
+    BundleMgrClient client;
+    std::string appName;
+    int32_t flags = 0;
+    int32_t userId =100;
+    ApplicationInfo appInfo;
+    auto ret = client.GetApplicationInfo(appName, flags, userId, appInfo);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_ProcessPreload_001
+ * @tc.desc: ProcessPreload
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_ProcessPreload_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    Want want;
+    auto ret = client.ProcessPreload(want);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_UpgradeAtomicService_001
+ * @tc.desc: UpgradeAtomicService
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_UpgradeAtomicService_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    Want want;
+    int32_t userId = 100;
+    client.UpgradeAtomicService(want, userId);
+    EXPECT_NE(client.impl_->bundleMgr_, nullptr);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_QueryAbilityInfo_003
+ * @tc.desc: QueryAbilityInfo
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_QueryAbilityInfo_003, TestSize.Level1)
+{
+    BundleMgrClient client;
+    Want want;
+    int32_t flags = 100;
+    int32_t userId = 100;
+    AbilityInfo abilityInfo;
+    auto ret = client.QueryAbilityInfo(want, flags, userId, abilityInfo);
+    EXPECT_EQ(ret, false);
+}
+
+/**
+ * @tc.name: BundleMgrClientTest_GetDefaultAppProxy_001
+ * @tc.desc: GetDefaultAppProxy
+ * @tc.type: FUNC
+ */
+HWTEST_F(BundleMgrClientTest, BundleMgrClientTest_GetDefaultAppProxy_001, TestSize.Level1)
+{
+    BundleMgrClient client;
+    auto ret = client.GetDefaultAppProxy();
+    EXPECT_NE(ret, nullptr);
+}
+}  // namespace AppExecFwk
+}  // namespace OHOS