Index: /trunk/src/VBox/HostServices/SharedClipboard/testcase/Makefile.kmk
===================================================================
--- /trunk/src/VBox/HostServices/SharedClipboard/testcase/Makefile.kmk	(revision 83686)
+++ /trunk/src/VBox/HostServices/SharedClipboard/testcase/Makefile.kmk	(revision 83687)
@@ -21,5 +21,5 @@
 if defined(VBOX_WITH_TESTCASES) && !defined(VBOX_ONLY_ADDITIONS) && !defined(VBOX_ONLY_SDK)
 
- PROGRAMS += tstClipboardServiceHost
+ PROGRAMS += tstClipboardServiceHost tstClipboardServiceImpl
 
  tstClipboardServiceHost_TEMPLATE = VBOXR3TSTEXE
@@ -31,4 +31,13 @@
 	tstClipboardServiceHost.cpp
 
+ $$(tstClipboardServiceHost_0_OUTDIR)/tstClipboardServiceHost.run: $$(tstClipboardServiceHost_1_STAGE_TARGET)
+	export VBOX_LOG_DEST=nofile; $(tstClipboardServiceHost_1_STAGE_TARGET) quiet
+	$(QUIET)$(APPEND) -t "$@" "done"
+
+ TESTING += $(tstClipboardServiceHost_0_OUTDIR)/tstClipboardServiceHost.run
+ ifndef VBOX_ONLY_SDK
+  OTHERS += $(tstClipboardServiceHost_0_OUTDIR)/tstClipboardServiceHost.run
+ endif
+
  if defined(VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS)
   tstClipboardServiceHost_DEFS    += VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
@@ -37,4 +46,21 @@
 	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-transfers.cpp \
 	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/ClipboardArea.cpp
+ endif
+
+ tstClipboardServiceImpl_TEMPLATE = VBOXR3TSTEXE
+ tstClipboardServiceImpl_DEFS     = VBOX_WITH_HGCM UNIT_TEST
+ tstClipboardServiceImpl_SOURCES  = \
+	../VBoxSharedClipboardSvc.cpp \
+	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-common.cpp \
+	$(PATH_ROOT)/src/VBox/HostServices/common/message.cpp \
+	tstClipboardServiceImpl.cpp
+
+ $$(tstClipboardServiceImpl_0_OUTDIR)/tstClipboardServiceImpl.run: $$(tstClipboardServiceImpl_1_STAGE_TARGET)
+	export VBOX_LOG_DEST=nofile; $(tstClipboardServiceImpl_1_STAGE_TARGET) quiet
+	$(QUIET)$(APPEND) -t "$@" "done"
+
+ TESTING += $(tstClipboardServiceImpl_0_OUTDIR)/tstClipboardServiceImpl.run
+ ifndef VBOX_ONLY_SDK
+  OTHERS += $(tstClipboardServiceImpl_0_OUTDIR)/tstClipboardServiceImpl.run
  endif
 
Index: /trunk/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardServiceImpl.cpp
===================================================================
--- /trunk/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardServiceImpl.cpp	(revision 83687)
+++ /trunk/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardServiceImpl.cpp	(revision 83687)
@@ -0,0 +1,108 @@
+/* $Id$ */
+/** @file
+ * Shared Clipboard host service implementation (backend) test case.
+ */
+
+/*
+ * Copyright (C) 2020 Oracle Corporation
+ *
+ * This file is part of VirtualBox Open Source Edition (OSE), as
+ * available from http://www.virtualbox.org. This file is free software;
+ * you can redistribute it and/or modify it under the terms of the GNU
+ * General Public License (GPL) as published by the Free Software
+ * Foundation, in version 2 as it comes in the "COPYING" file of the
+ * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
+ * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
+ */
+
+#include "../VBoxSharedClipboardSvc-internal.h"
+
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+
+#include <iprt/assert.h>
+#include <iprt/string.h>
+#include <iprt/test.h>
+
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad (VBOXHGCMSVCFNTABLE *ptable);
+
+static SHCLCLIENT g_Client;
+static VBOXHGCMSVCHELPERS g_Helpers = { NULL };
+
+/** Simple call handle structure for the guest call completion callback */
+struct VBOXHGCMCALLHANDLE_TYPEDEF
+{
+    /** Where to store the result code */
+    int32_t rc;
+};
+
+/** Call completion callback for guest calls. */
+static DECLCALLBACK(int) callComplete(VBOXHGCMCALLHANDLE callHandle, int32_t rc)
+{
+    callHandle->rc = rc;
+    return VINF_SUCCESS;
+}
+
+static int setupTable(VBOXHGCMSVCFNTABLE *pTable)
+{
+    pTable->cbSize = sizeof(*pTable);
+    pTable->u32Version = VBOX_HGCM_SVC_VERSION;
+    g_Helpers.pfnCallComplete = callComplete;
+    pTable->pHelpers = &g_Helpers;
+    return VBoxHGCMSvcLoad(pTable);
+}
+
+int ShClSvcImplInit(void) { return VINF_SUCCESS; }
+void ShClSvcImplDestroy(void) { }
+int ShClSvcImplDisconnect(PSHCLCLIENT) { return VINF_SUCCESS; }
+int ShClSvcImplConnect(PSHCLCLIENT, bool) { return VINF_SUCCESS; }
+int ShClSvcImplFormatAnnounce(PSHCLCLIENT, SHCLFORMATS) { AssertFailed(); return VINF_SUCCESS; }
+int ShClSvcImplReadData(PSHCLCLIENT, PSHCLCLIENTCMDCTX, SHCLFORMAT, void *, uint32_t, unsigned int *) { AssertFailed(); return VERR_WRONG_ORDER; }
+int ShClSvcImplWriteData(PSHCLCLIENT, PSHCLCLIENTCMDCTX, SHCLFORMAT, void *, uint32_t) { AssertFailed(); return VINF_SUCCESS; }
+int ShClSvcImplSync(PSHCLCLIENT) { return VINF_SUCCESS; }
+
+static void testAnnounceAndReadData(void)
+{
+    struct VBOXHGCMSVCPARM parms[2];
+    VBOXHGCMSVCFNTABLE table;
+    int rc;
+
+    RTTestISub("Setting up client ...");
+    rc = setupTable(&table);
+    RTTESTI_CHECK_MSG_RETV(RT_SUCCESS(rc), ("rc=%Rrc\n", rc));
+    /* Unless we are bidirectional the host message requests will be dropped. */
+    HGCMSvcSetU32(&parms[0], VBOX_SHCL_MODE_BIDIRECTIONAL);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_MODE, 1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+    rc = shClSvcClientInit(&g_Client, 1 /* clientId */);
+    RTTESTI_CHECK_RC_OK(rc);
+}
+
+int main(int argc, char *argv[])
+{
+    /*
+     * Init the runtime, test and say hello.
+     */
+    const char *pcszExecName;
+    NOREF(argc);
+    pcszExecName = strrchr(argv[0], '/');
+    pcszExecName = pcszExecName ? pcszExecName + 1 : argv[0];
+    RTTEST hTest;
+    RTEXITCODE rcExit = RTTestInitAndCreate(pcszExecName, &hTest);
+    if (rcExit != RTEXITCODE_SUCCESS)
+        return rcExit;
+    RTTestBanner(hTest);
+
+    /* Don't let assertions in the host service panic (core dump) the test cases. */
+    RTAssertSetMayPanic(false);
+
+    /*
+     * Run the tests.
+     */
+    testAnnounceAndReadData();
+
+    /*
+     * Summary
+     */
+    return RTTestSummaryAndDestroy(hTest);
+}
+