diff --git a/tests/common b/tests/common
index 71661e95..c6802c3d 100644
--- a/tests/common
+++ b/tests/common
@@ -169,6 +169,9 @@ run_check()
 
 # same as run_check but the stderr+stdout output is duplicated on stdout and
 # can be processed further
+#
+# NOTE: If this function is called on btrfs related commands, caller should
+#	filter the output, as INSTRUMENT can easily pollute the output.
 run_check_stdout()
 {
 	local spec
@@ -636,6 +639,16 @@ check_min_kernel_version()
 	return 0
 }
 
+# Get subvolume id for specified path
+_get_subvolid()
+{
+	# run_check_stdout may have INSTRUMENT polluting the output, we need to
+	# filter the output
+	run_check_stdout "$TOP/btrfs" inspect-internal rootid "$1" | \
+		grep -e "^[[:digit:]]\+$"
+
+}
+
 # compare running kernel version to the given parameter, return success
 # if running is newer than requested (let caller decide if to fail or skip)
 # $1: minimum version of running kernel in major.minor format (eg. 4.19)
diff --git a/tests/misc-tests/004-shrink-fs/test.sh b/tests/misc-tests/004-shrink-fs/test.sh
index 74150063..5ec51490 100755
--- a/tests/misc-tests/004-shrink-fs/test.sh
+++ b/tests/misc-tests/004-shrink-fs/test.sh
@@ -11,11 +11,18 @@ check_prereq btrfs
 
 setup_root_helper
 
+_get_min_dev_size()
+{
+	size=$(run_check_stdout $SUDO_HELPER "$TOP/btrfs" inspect-internal \
+		min-dev-size ${1:+--id "$1"} "$TEST_MNT" |		   \
+		grep -e "^[[:digit:]]\+.*)$" | cut -d ' ' -f 1)
+	echo "$size"
+}
+
 # Optionally take id of the device to shrink
 shrink_test()
 {
-	min_size=$(run_check_stdout $SUDO_HELPER "$TOP/btrfs" inspect-internal min-dev-size ${1:+--id "$1"}  "$TEST_MNT")
-	min_size=$(echo "$min_size" | cut -d ' ' -f 1)
+	min_size=$(_get_min_dev_size "$1")
 	_log "min size = ${min_size}"
 	if [ -z "$min_size" ]; then
 		_fail "Failed to parse minimum size"
diff --git a/tests/misc-tests/009-subvolume-sync-must-wait/test.sh b/tests/misc-tests/009-subvolume-sync-must-wait/test.sh
index 91dcebbb..ef27b368 100755
--- a/tests/misc-tests/009-subvolume-sync-must-wait/test.sh
+++ b/tests/misc-tests/009-subvolume-sync-must-wait/test.sh
@@ -31,7 +31,7 @@ done
 run_check $SUDO_HELPER "$TOP/btrfs" subvolume list .
 run_check $SUDO_HELPER "$TOP/btrfs" subvolume list -d .
 
-idtodel=`run_check_stdout $SUDO_HELPER "$TOP/btrfs" inspect-internal rootid snap3`
+idtodel=$(_get_subvolid snap3)
 
 # delete, sync after some time
 run_check $SUDO_HELPER "$TOP/btrfs" subvolume delete -c snap3
diff --git a/tests/misc-tests/013-subvolume-sync-crash/test.sh b/tests/misc-tests/013-subvolume-sync-crash/test.sh
index 64ba9959..8d4e7603 100755
--- a/tests/misc-tests/013-subvolume-sync-crash/test.sh
+++ b/tests/misc-tests/013-subvolume-sync-crash/test.sh
@@ -32,7 +32,7 @@ done
 run_check $SUDO_HELPER "$TOP/btrfs" subvolume list .
 run_check $SUDO_HELPER "$TOP/btrfs" subvolume list -d .
 
-idtodel=`run_check_stdout $SUDO_HELPER "$TOP/btrfs" inspect-internal rootid snap3`
+idtodel=`$SUDO_HELPER "$TOP/btrfs" inspect-internal rootid snap3`
 
 # delete, sync after some time
 run_check $SUDO_HELPER "$TOP/btrfs" subvolume delete -c snap*
diff --git a/tests/misc-tests/024-inspect-internal-rootid/test.sh b/tests/misc-tests/024-inspect-internal-rootid/test.sh
index b1c804d9..119dd1cb 100755
--- a/tests/misc-tests/024-inspect-internal-rootid/test.sh
+++ b/tests/misc-tests/024-inspect-internal-rootid/test.sh
@@ -21,20 +21,13 @@ run_check touch file1
 run_check touch dir/file2
 run_check touch sub/file3
 
-id1=$(run_check_stdout "$TOP/btrfs" inspect-internal rootid .) \
-	|| { echo $id1; exit 1; }
-id2=$(run_check_stdout "$TOP/btrfs" inspect-internal rootid sub) \
-	|| { echo $id2; exit 1; }
-id3=$(run_check_stdout "$TOP/btrfs" inspect-internal rootid sub/subsub) \
-	|| { echo $id3; exit 1; }
-id4=$(run_check_stdout "$TOP/btrfs" inspect-internal rootid dir) \
-	|| { echo $id4; exit 1; }
-id5=$(run_check_stdout "$TOP/btrfs" inspect-internal rootid file1) \
-	|| { echo $id5; exit 1; }
-id6=$(run_check_stdout "$TOP/btrfs" inspect-internal rootid dir/file2) \
-	|| { echo $id6; exit 1; }
-id7=$(run_check_stdout "$TOP/btrfs" inspect-internal rootid sub/file3) \
-	|| { echo $id7; exit 1; }
+id1=$(_get_subvolid .) || { echo $id1; exit 1; }
+id2=$(_get_subvolid sub) || { echo $id2; exit 1; }
+id3=$(_get_subvolid sub/subsub) || { echo $id3; exit 1; }
+id4=$(_get_subvolid dir) || { echo $id4; exit 1; }
+id5=$(_get_subvolid file1) || { echo $id5; exit 1; }
+id6=$(_get_subvolid dir/file2) || { echo $id6; exit 1; }
+id7=$(_get_subvolid sub/file3) || { echo $id7; exit 1; }
 
 if ! ([ "$id1" -ne "$id2" ] && [ "$id1" -ne "$id3" ] && [ "$id2" -ne "$id3" ]); then
 	_fail "inspect-internal rootid: each subvolume must have different id"
diff --git a/tests/misc-tests/031-qgroup-parent-child-relation/test.sh b/tests/misc-tests/031-qgroup-parent-child-relation/test.sh
index f8529058..53bc953e 100755
--- a/tests/misc-tests/031-qgroup-parent-child-relation/test.sh
+++ b/tests/misc-tests/031-qgroup-parent-child-relation/test.sh
@@ -18,10 +18,10 @@ run_check $SUDO_HELPER "$TOP/btrfs" qgroup assign 0/5 1/0 "$TEST_MNT"
 run_check $SUDO_HELPER "$TOP/btrfs" quota rescan -w "$TEST_MNT"
 
 run_check_stdout $SUDO_HELPER "$TOP/btrfs" qgroup show --sort=-qgroupid \
-	-p "$TEST_MNT" | tail -n 1 | grep -q "1/0" \
+	-p "$TEST_MNT" | grep -q "1/0" \
 	|| _fail "parent qgroup check failed, please check the log"
 run_check_stdout $SUDO_HELPER "$TOP/btrfs" qgroup show --sort=qgroupid \
-	-c "$TEST_MNT" | tail -n 1 | grep -q "0/5" \
+	-c "$TEST_MNT" | grep -q "0/5" \
 	|| _fail "child qgroup check failed, please check the log"
 
 run_check_umount_test_dev "$TEST_MNT"