Truncate test output to exclude test instructions

This adds markers right before starting a test case and right after it
completed, which are then used to truncate the output of the test case
so that it doesn’t include any instructions related to the testing
framework, as these aren’t relevant to users inspecting the test ouptut.

Author: pluehne

test/testlib.sh

@@ -144,20 +144,28 @@ begin_test () {
   # allow the subshell to exit non-zero without exiting this process
   set -x +e
   before_time=$(date '+%s.%3N')
+
+  # Marker to truncate the actual test output later
+  echo "begin_test_truncate_marker" > /dev/null
 }
 
 report_failure_output () {
-  (
-    sed 's/^/    /' <"$TRASHDIR/out" |
-    grep -a -v -e '^\+ end_test' -e '^+ set +x' |
-    sed 's/[+] test_status=/test failed. last command exited with /' |
-    sed 's/^/    /'
-  ) 1>&2
+  # Truncate the test output to exclude testing-related instructions
+  echo "$(<"$TRASHDIR/out")" \
+    | sed '0,/begin_test_truncate_marker/d' \
+    | sed -n '/end_test_truncate_marker/q;p' | head -n -2 \
+    | sed 's/^/    /' \
+    1>&2
+  echo -e "\nTest failed. The last command exited with exit code $test_status." 1>&2
 }
 
 # Mark the end of a test.
 end_test () {
   test_status="${1:-$?}"
+
+  # Marker to truncate the actual test output later
+  echo "end_test_truncate_marker" > /dev/null
+
   after_time=$(date '+%s.%3N')
   elapsed_time=$(echo "scale=3; $after_time - $before_time" | bc)
   set +x -e