test: Make log truncation test more robust

test/pasta_options/log_to_file checks that pasta truncates its log file
when started.  It does that by starting pasta with a log file once, then
starting it again and checking that after the second round, the log file
has only one line: the startup banner from the second invocation.

However, this test will break if the second invocation logs any additional
messages at startup.  This can easily happen on a host with multiple
network interfaces due to the "Multiple default route" informational
messages added in 639fdf06e ("netlink: Fix selection of template
interface").  I believe it could also happen on a host without IPv6
connectivity due to the "Couldn't pick external interface" messages, though
I haven't confirmed this.

Make the log file test more robust, by not testing for a single line, but
instead explicitly testing for the PID of the second pasta invocation in
the banner line.

Link: https://bugs.passt.top/show_bug.cgi?id=88
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/test/pasta_options/log_to_file b/test/pasta_options/log_to_file
index f100216..fe50e50 100644
--- a/test/pasta_options/log_to_file
+++ b/test/pasta_options/log_to_file
@@ -37,8 +37,9 @@ passt	./pasta -l __LOG_FILE__ -- /bin/true
 check	[ -s __LOG_FILE__ ]
 
 test	Log truncated on creation
-passt	./pasta -l __LOG_FILE__ -- /bin/true
-check	[ $(cat __LOG_FILE__ | wc -l) -eq 1 ]
+passt	./pasta -l __LOG_FILE__ -- /bin/true & wait
+pout	PID2 echo $!
+check	head -1 __LOG_FILE__ | grep '^pasta .* [(]__PID2__[)]$'
 
 test	Maximum log size
 passtb	./pasta --config-net -d -f -l __LOG_FILE__ --log-size $((100 * 1024)) -- sh -c 'while true; do tcp_crr --nolog -P 10001 -C 10002 -6; done'