diff --git a/README.overlay b/README.overlay
index 30b5ddb2..39e25ada 100644
--- a/README.overlay
+++ b/README.overlay
@@ -50,3 +50,18 @@ In the example above, MOUNT_OPTIONS will be used to mount the base scratch fs,
 TEST_FS_MOUNT_OPTS will be used to mount the base test fs,
 OVERLAY_MOUNT_OPTIONS will be used to mount both test and scratch overlay and
 OVERLAY_FSCK_OPTIONS will be used to check both test and scratch overlay.
+
+
+Unionmount Testsuite
+====================
+
+xfstests can be used as a test harness to run unionmount testsuite test cases
+and provide extended test coverage for overlayfs.
+
+To enable running unionmount testsuite, clone the git repository from:
+  https://github.com/amir73il/unionmount-testsuite.git
+under the xfstests src directory, or set the environment variable
+UNIONMOUNT_TESTSUITE to the local path where the repository was cloned.
+
+Run './check -overlay -g overlay/union' to execute all the unionmount testsuite
+test cases.
diff --git a/common/config b/common/config
index 8023273d..e356bcda 100644
--- a/common/config
+++ b/common/config
@@ -71,6 +71,8 @@ export OVL_LOWER="ovl-lower"
 export OVL_WORK="ovl-work"
 # overlay mount point parent must be the base fs root
 export OVL_MNT="ovl-mnt"
+# By default unionmount-testsuite is expected under src
+export UNIONMOUNT_TESTSUITE=${UNIONMOUNT_TESTSUITE:=$here/src/unionmount-testsuite}
 
 # From e2fsprogs/e2fsck/e2fsck.h:
 # Exit code used by fsck-type programs
diff --git a/common/overlay b/common/overlay
index f8e1e27f..5e6a7e0f 100644
--- a/common/overlay
+++ b/common/overlay
@@ -363,3 +363,57 @@ _repair_overlay_scratch_fs()
 	esac
 	return $res
 }
+
+# This test requires that unionmount testsuite is installed at
+# $UNIONMOUNT_TESTSUITE and that it supports configuring layers and overlay
+# mount paths via UNIONMOUNT_* environment variables.
+_require_unionmount_testsuite()
+{
+	[ -x "$UNIONMOUNT_TESTSUITE/run" ] || \
+		_notrun "unionmount testsuite required."
+
+	# Verify that UNIONMOUNT_* vars are supported
+	local usage=`UNIONMOUNT_BASEDIR=_ "$UNIONMOUNT_TESTSUITE/run" 2>&1`
+	echo $usage | grep -wq "UNIONMOUNT_BASEDIR" || \
+		_notrun "newer version of unionmount testsuite required."
+}
+
+_unionmount_testsuite_run()
+{
+	[ "$FSTYP" = overlay ] || \
+		_notrun "Filesystem $FSTYP not supported with unionmount testsuite."
+
+	# Provide the mounted base fs for upper and lower dirs and the
+	# overlay mount point.
+	# unionmount testsuite will perform the overlay mount.
+	# test fs is used for lower layer in non-samefs runs.
+	# scratch fs is used for upper layer in non-samefs runs and
+	# for both layers in samefs runs.
+	if (echo $* | grep -qv samefs) ; then
+		_overlay_base_test_mount
+		export UNIONMOUNT_LOWERDIR=$OVL_BASE_TEST_DIR/union
+	fi
+	export UNIONMOUNT_BASEDIR=$OVL_BASE_SCRATCH_MNT/union
+
+	_scratch_mkfs
+	rm -rf $UNIONMOUNT_BASEDIR $UNIONMOUNT_LOWERDIR
+	mkdir -p $UNIONMOUNT_BASEDIR $UNIONMOUNT_LOWERDIR
+
+	cd $UNIONMOUNT_TESTSUITE
+	echo "run $* ..." > $seqres.full
+	./run $* >> $seqres.full || \
+		echo "unionmount testsuite failed! see $seqres.full for details."
+}
+
+_unionmount_testsuite_cleanup()
+{
+	cd /
+	rm -f $tmp.*
+
+	[ -n "$UNIONMOUNT_BASEDIR" ] || return 0
+
+	# Cleanup overlay mount after unionmount testsuite run
+	cd $UNIONMOUNT_TESTSUITE
+	echo "run --clean-up ..." >> $seqres.full
+	./run --clean-up >> $seqres.full 2>&1
+}
diff --git a/tests/overlay/100 b/tests/overlay/100
new file mode 100755
index 00000000..a2e82dfa
--- /dev/null
+++ b/tests/overlay/100
@@ -0,0 +1,38 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2020 CTERA Networks. All Rights Reserved.
+#
+# FS QA Test 100
+#
+# Run unionmount testsuite to verify correctness
+# with single lower layer on same fs as upper
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_unionmount_testsuite_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+_supported_fs overlay
+_supported_os Linux
+_require_scratch
+_require_unionmount_testsuite
+
+_unionmount_testsuite_run --ov --samefs --verify
+
+# success, all done
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/overlay/100.out b/tests/overlay/100.out
new file mode 100644
index 00000000..798c0136
--- /dev/null
+++ b/tests/overlay/100.out
@@ -0,0 +1,2 @@
+QA output created by 100
+Silence is golden
diff --git a/tests/overlay/101 b/tests/overlay/101
new file mode 100755
index 00000000..2b3a75d4
--- /dev/null
+++ b/tests/overlay/101
@@ -0,0 +1,39 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2020 CTERA Networks. All Rights Reserved.
+#
+# FS QA Test 101
+#
+# Run unionmount testsuite to verify correctness
+# with single lower layer not on same fs as upper
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_unionmount_testsuite_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+_supported_fs overlay
+_supported_os Linux
+_require_test
+_require_scratch
+_require_unionmount_testsuite
+
+_unionmount_testsuite_run --ov --verify
+
+# success, all done
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/overlay/101.out b/tests/overlay/101.out
new file mode 100644
index 00000000..e651a915
--- /dev/null
+++ b/tests/overlay/101.out
@@ -0,0 +1,2 @@
+QA output created by 101
+Silence is golden
diff --git a/tests/overlay/102 b/tests/overlay/102
new file mode 100755
index 00000000..2dddbe50
--- /dev/null
+++ b/tests/overlay/102
@@ -0,0 +1,40 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2020 CTERA Networks. All Rights Reserved.
+#
+# FS QA Test 102
+#
+# Run unionmount testsuite to verify correctness
+# with single lower layer not on same fs as upper
+# with xino enabled
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_unionmount_testsuite_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+_supported_fs overlay
+_supported_os Linux
+_require_test
+_require_scratch
+_require_unionmount_testsuite
+
+_unionmount_testsuite_run --ov --xino --verify
+
+# success, all done
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/overlay/102.out b/tests/overlay/102.out
new file mode 100644
index 00000000..86dd1f96
--- /dev/null
+++ b/tests/overlay/102.out
@@ -0,0 +1,2 @@
+QA output created by 102
+Silence is golden
diff --git a/tests/overlay/group b/tests/overlay/group
index 0cebcad0..267161f4 100644
--- a/tests/overlay/group
+++ b/tests/overlay/group
@@ -77,3 +77,6 @@
 072 auto quick copyup hardlink
 073 auto quick whiteout
 074 auto quick exportfs dangerous
+100 auto quick union samefs
+101 auto quick union nonsamefs
+102 auto quick union nonsamefs xino
