Currently, the test case throtl/004 assumes that the test target device
is null_blk. When it verifies the dd command error message, it checks
the string "/dev/dev_nullb" also. However, this test will fail when the
test case is extended to support scsi_debug.

To avoid the failure, remove dependency on the specific device name.
Save the dd command error output to the FULL file, and check only the
error message part in the FULL file.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
---
 tests/throtl/004     | 4 +++-
 tests/throtl/004.out | 3 +--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/tests/throtl/004 b/tests/throtl/004
index d623097..777afcf 100755
--- a/tests/throtl/004
+++ b/tests/throtl/004
@@ -22,7 +22,7 @@ test() {
 
 	{
 		echo "$BASHPID" > "$CGROUP2_DIR/$THROTL_DIR/cgroup.procs"
-		_throtl_issue_io write 10M 1
+		_throtl_issue_io write 10M 1 &>> "$FULL"
 	} &
 
 	sleep 0.6
@@ -30,5 +30,7 @@ test() {
 	wait $!
 
 	_clean_up_throtl
+
+	grep --only-matching "Input/output error" "$FULL"
 	echo "Test complete"
 }
diff --git a/tests/throtl/004.out b/tests/throtl/004.out
index e76ec3a..3997531 100644
--- a/tests/throtl/004.out
+++ b/tests/throtl/004.out
@@ -1,4 +1,3 @@
 Running throtl/004
-dd: error writing '/dev/dev_nullb': Input/output error
-1
+Input/output error
 Test complete
-- 
2.51.0