tools/rtla: Add test engine support for unexpected output

Add a check() parameter to indicate which text must not appear in the
output.

Simplify the code so that we can print failures as they happen rather
than trying to figure out what went wrong after printing "not ok".  This
also means that "not ok" gets printed after the info rather than before,
which seems more intuitive anyway.

Cc: John Kacur <jkacur@redhat.com>
Cc: Costa Shulyupin <costa.shul@redhat.com>
Link: https://lore.kernel.org/20250907022325.243930-7-crwood@redhat.com
Reviewed-by: Tomas Glozar  <tglozar@redhat.com>
Signed-off-by: Crystal Wood <crwood@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

tools/tracing/rtla/tests/engine.sh

@@ -43,6 +43,7 @@ check() {
 	tested_command=$1
 	expected_exitcode=${3:-0}
 	expected_output=$4
+	unexpected_output=$5
 	# Simple check: run rtla with given arguments and test exit code.
 	# If TEST_COUNT is set, run the test. Otherwise, just count.
 	ctr=$(($ctr + 1))
@@ -53,24 +54,33 @@ check() {
 		# Run rtla; in case of failure, include its output as comment
 		# in the test results.
 		result=$(eval stdbuf -oL $TIMEOUT "$RTLA" $2 2>&1); exitcode=$?
+		failbuf=''
+		fail=0
+
 		# Test if the results matches if requested
-		if [ -n "$expected_output" ]
+		if [ -n "$expected_output" ] && ! grep -qE "$expected_output" <<< "$result"
 		then
-			grep -E "$expected_output" <<< "$result" > /dev/null; grep_result=$?
-		else
-			grep_result=0
+			fail=1
+			failbuf+=$(printf "# Output match failed: \"%s\"" "$expected_output")
+			failbuf+=$'\n'
 		fi
 
-		if [ $exitcode -eq $expected_exitcode ] && [ $grep_result -eq 0 ]
+		if [ -n "$unexpected_output" ] && grep -qE "$unexpected_output" <<< "$result"
+		then
+			fail=1
+			failbuf+=$(printf "# Output non-match failed: \"%s\"" "$unexpected_output")
+			failbuf+=$'\n'
+		fi
+
+		if [ $exitcode -eq $expected_exitcode ] && [ $fail -eq 0 ]
 		then
 			echo "ok $ctr - $1"
 		else
-			echo "not ok $ctr - $1"
 			# Add rtla output and exit code as comments in case of failure
+			echo "not ok $ctr - $1"
+			echo -n "$failbuf"
 			echo "$result" | col -b | while read line; do echo "# $line"; done
 			printf "#\n# exit code %s\n" $exitcode
-			[ -n "$expected_output" ] && [ $grep_result -ne 0 ] && \
-				printf "# Output match failed: \"%s\"\n" "$expected_output"
 		fi
 	fi
 }