Fix: Tests: `test_exclusion` passing for the wrong reason

Issue
=====
The following commit added `-i` and `-w` flags to the test app arguments
of the `test_exclusion` tests:
  commit 6c4a91d639747f260ab46decebc50998ef063712
  Author: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  Date:   Mon Aug 26 14:22:06 2019 -0400

      tests: gen-ust-events: use options instead of arguments

      Remove argument dependency and ease usage of features individually.

The `gen-ust-nevents` was not modified to support those flags. I suspect this
mistake was caused by the name similarity of the `gen-ust-nevents` and the
`gen-ust-events` test applications.

We ended up calling the following command:
  ./gen-ust-nevents -i 100 -w -1

When called with such arguments the `gen-ust-nevents` parsed the first
argument (`-i`) using `atoi()` which retuned 0. This was interpreted as
the number of iterations requested by the user so the app immediately
exited without generating any events.

So, the test was not seeing any of the excluded events in the trace
which was then considered as a successful result but no events were ever
excluded because none were generated in the first place.

Solution
========
Remove the use of `-i` and `-w` flags.

I also added a `dry_run` test to confirm that we do indeed get events
when exclusions are not used to prevent this error from happening in the
future.

Notes
=====
- I changed the wildcard used in the enable-event command so to only
  enable events from the testapp and not the `lttng_ust_statedump:` events
  as those are generated even if we didnt' ask for them.

- I add a stderr redirection to `/dev/null` in the trace reading
  pipeline because we now end up with traces with no events. This has
  changed because we now only enable events from the application (see
  previous note).

- In a future commit, I will change the `gen-ust-nevents` application to
  take those `-i` and `-w` flags.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: Id37dcd59a18b3401d97439bce1191a8c5cac87d5
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/tests/regression/tools/exclusion/test_exclusion b/tests/regression/tools/exclusion/test_exclusion
index 6cd808c6d7ac13101c9ac87a5aa26614d0f7dea9..d295535828831a6086d86e6c25d6cb2fa412ef79 100755 (executable)
--- a/tests/regression/tools/exclusion/test_exclusion
+++ b/tests/regression/tools/exclusion/test_exclusion
@@ -16,7 +16,7 @@ TESTAPP_NAME="gen-ust-nevents"
 TESTAPP_BIN="$TESTAPP_PATH/$TESTAPP_NAME/$TESTAPP_NAME"
 NR_ITER=100
 NR_USEC_WAIT=1
-NUM_TESTS=149
+NUM_TESTS=178
 
 source $TESTDIR/utils/utils.sh
 
@@ -25,12 +25,45 @@ function enable_ust_lttng_all_event_exclusion()
        sess_name="$1"
        exclusion="$2"
 
-       $TESTDIR/../src/bin/lttng/$LTTNG_BIN enable-event -a -s $sess_name -u -x "$exclusion"
+       $TESTDIR/../src/bin/lttng/$LTTNG_BIN enable-event -u "tp:*" -s $sess_name -x "$exclusion"
 }
 
 function run_apps
 {
-        $TESTAPP_BIN -i $NR_ITER -w $NR_USEC_WAIT >/dev/null 2>&1
+       $TESTAPP_BIN $NR_ITER $NR_USEC_WAIT >/dev/null 2>&1
+       ok $? "Running test application"
+}
+
+# Testing for the absence of an event when testing exclusion is tricky. An
+# event could be absent because our exclusion mechanism works but also because
+# the event was not generate in the first place. This function test the ability
+# of our test suite to generate events.
+function dry_run
+{
+       trace_path=$(mktemp -d)
+
+       # Create session
+       create_lttng_session_ok $SESSION_NAME $trace_path
+
+       $TESTDIR/../src/bin/lttng/$LTTNG_BIN enable-event -u "tp:*" -s $SESSION_NAME > /dev/null
+       ok $? "Enabling events without exclusion"
+
+       # Trace apps
+       start_lttng_tracing_ok $SESSION_NAME
+       run_apps
+       stop_lttng_tracing_ok $SESSION_NAME
+
+       nb_events=$(babeltrace $trace_path | wc -l)
+       if [ "$nb_events" -ne "0" ]; then
+               ok 0 "Events were found during the dry run without exclusion"
+       else
+               fail "No events were found during the dry run without exclusion"
+       fi
+
+       rm -rf $trace_path
+
+       # Destroy session
+       destroy_lttng_session_ok $SESSION_NAME
 }
 
 function test_exclusion
@@ -53,7 +86,7 @@ function test_exclusion
        # Destroy session
        destroy_lttng_session_ok $SESSION_NAME
 
-       stats=`babeltrace $trace_path | $STATS_BIN --tracepoint "$event_name_expected_to_be_missing" | grep -v index`
+       stats=`babeltrace $trace_path | $STATS_BIN --tracepoint "$event_name_expected_to_be_missing" | grep -v index 2> /dev/null`
        if [ ! -z "$stats" ]; then
                fail "Excluded event \"$event_name_expected_to_be_missing\" was found in trace!"
        else
@@ -87,6 +120,8 @@ print_test_banner $TEST_DESC
 
 start_lttng_sessiond
 
+dry_run
+
 test_exclusion 'tp:tptest2' 'tp:tptest2'
 test_exclusion 'tp:tptest3' 'tp:tptest3'
 test_exclusion 'tp:tptest*' 'tp:tptest1'