tests: fix spurious failure due to I/O buffering

* tests/parallel-tests-interrupt.tap: Ensure the dummy test script
`foo.test' flushes its standard output before starting to grep the
log file where such output is being redirected by the parallel test
harness.  Since we are at it, improve this same dummy script to
better catch unexpected behaviours and results.

Reported by Jim Meyering in automake bug#10418.

diff --git a/tests/parallel-tests-interrupt.tap b/tests/parallel-tests-interrupt.tap
index ffe407430f8b7b844863f91cea72f606ae1be4d2..74b418dd7b65ae11deb6d67794eb252ba1df5604 100755 (executable)
--- a/tests/parallel-tests-interrupt.tap
+++ b/tests/parallel-tests-interrupt.tap
@@ -1,5 +1,5 @@
 #! /bin/sh
-# Copyright (C) 2011 Free Software Foundation, Inc.
+# Copyright (C) 2011, 2012 Free Software Foundation, Inc.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -45,27 +45,45 @@ echo $$ > pid
 END
 
 cat > foo.test << 'END'
-#!/bin/sh
-
-echo "foo is starting to run"
-
-ls -l >&9 || exit 99
-
-test $sig -gt 0 || {
-  echo "Bailout! \$sig not exported to test script" >&9
-  exit 99
+#!/bin/sh -e
+
+# We expect the test driver to be terminated by a signal, and so
+# to exit with non-zero status, thus causing "make check" to fail.
+# Exiting with status 0 from this test script is thus a good way to
+# make unexpected behaviours more evident, since this will likely
+# cause and unexpected success in "make check".
+trap 'exit 0' 0;
+stop_test () { exit 0; }
+
+# We need the "foo is starting to run" string flushed to standard output
+# ASAP, because we are soon going to grep for that string in the log file
+# where the test driver is redirecting this script's stdout.  The safest
+# way force this flushing portably is to rely on perl I/O capabilities.
+$PERL -e 'BEGIN { $| = 1 }; print "foo is starting to run\n"' || stop_test
+
+ls -l >&9 || stop_test
+
+bailout ()
+{
+  # Print this to the original stdout (saved in the fd 9), so that the
+  # emitted "Bail out!" directive will be interpreted by the test driver
+  # running the Automake testsuite.
+  echo "Bail out! $*" >&9
+  stop_test
 }
 
+test $sig -gt 0 || bailout "\$sig not exported to test script"
+
 res=ok; cat foo.log >&9 || res="not ok"
 echo "$res - logfile created and readable [SIG $sig]" >&9
 
-res=ok; grep '^foo is starting to run$' foo.log >&2 || res='not ok'
+res=ok; grep '^foo is starting to run$' foo.log >&9 || res='not ok'
 echo "$res - logfile contains output from test script [SIG $sig]" >&9
 
-cat pid >&9 \
-  || echo "Bailout! cannot get PID of test driver" >&9
-kill -$sig `cat pid` \
-  || echo "Bailout! cannot send signal $sig to test driver" >&9
+cat pid >&9 || bailout "cannot get PID of test driver"
+kill -$sig `cat pid` || bailout "cannot send signal $sig to test driver"
+
+stop_test
 END
 chmod a+x foo.test
 
@@ -85,7 +103,7 @@ for sig in $trapped_signals; do
     continue
   fi
   rm -f pid fail *.log
-  r=ok; env sig=$sig $MAKE check && r='not ok'
+  r=ok; env PERL="$PERL" sig="$sig" $MAKE check && r='not ok'
   echo "$r - signal $sig to test driver causes \"make check\" to fail"
   ls -l
   # These files shouldn't exist, but in case they do, their content might