test,travis: dump a screenshot for hanging GUI tests

For some reason the wireshark GUI tests hang on the Travis OS X builds,
but I could not reproduce it locally. It turns out than an error dialog
was present, but I could not know that without the screenshot.

Change-Id: Idf897d33b4fddf3c19c69ebcea60b629f1ca9368
Reviewed-on: https://code.wireshark.org/review/31682
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot
Reviewed-by: Peter Wu <peter@lekensteyn.nl>

.travis.yml

@@ -132,3 +132,4 @@ script:
 after_script:
   - if [ -f run/tshark ]; then run/tshark --version; fi
   - if [ -f run/RelWithDebInfo/tshark.exe ]; then run/RelWithDebInfo/tshark.exe --version; fi
+  - ../test/travis-upload-artifacts.sh

test/fixtures_ws.py

@@ -8,6 +8,7 @@
 #
 '''Fixtures that are specific to Wireshark.'''
 
+from contextlib import contextmanager
 import os
 import re
 import subprocess
@@ -302,3 +303,34 @@ def unicode_env(home_path, make_env):
         env=env,
         pluginsdir=pluginsdir
     )
+
+
+@fixtures.fixture(scope='session')
+def make_screenshot():
+    '''Creates a screenshot and save it to a file. Intended for CI purposes.'''
+    def make_screenshot_real(filename):
+        try:
+            if sys.platform == 'darwin':
+                subprocess.check_call(['screencapture', filename])
+            else:
+                print("Creating a screenshot on this platform is not supported")
+                return
+            size = os.path.getsize(filename)
+            print("Created screenshot %s (%d bytes)" % (filename, size))
+        except (subprocess.CalledProcessError, OSError) as e:
+            print("Failed to take screenshot:", e)
+    return make_screenshot_real
+
+
+@fixtures.fixture
+def make_screenshot_on_error(request, make_screenshot):
+    '''Writes a screenshot when a process times out.'''
+    @contextmanager
+    def make_screenshot_on_error_real():
+        try:
+            yield
+        except subprocess.TimeoutExpired:
+            filename = request.instance.filename_from_id('screenshot.png')
+            make_screenshot(filename)
+            raise
+    return make_screenshot_on_error_real

test/suite_capture.py

@@ -471,26 +471,30 @@ def check_dumpcap_pcapng_sections(cmd_dumpcap, cmd_tshark, capture_file):
 @fixtures.mark_usefixtures('test_env')
 @fixtures.uses_fixtures
 class case_wireshark_capture(subprocesstest.SubprocessTestCase):
-    def test_wireshark_capture_10_packets_to_file(self, wireshark_k, check_capture_10_packets):
+    def test_wireshark_capture_10_packets_to_file(self, wireshark_k, check_capture_10_packets, make_screenshot_on_error):
         '''Capture 10 packets from the network to a file using Wireshark'''
-        check_capture_10_packets(self, cmd=wireshark_k)
+        with make_screenshot_on_error():
+            check_capture_10_packets(self, cmd=wireshark_k)
 
     # Wireshark doesn't currently support writing to stdout while capturing.
     # def test_wireshark_capture_10_packets_to_stdout(self, wireshark_k, check_capture_10_packets):
     #     '''Capture 10 packets from the network to stdout using Wireshark'''
     #     check_capture_10_packets(self, cmd=wireshark_k, to_stdout=True)
 
-    def test_wireshark_capture_from_fifo(self, wireshark_k, check_capture_fifo):
+    def test_wireshark_capture_from_fifo(self, wireshark_k, check_capture_fifo, make_screenshot_on_error):
         '''Capture from a fifo using Wireshark'''
-        check_capture_fifo(self, cmd=wireshark_k)
+        with make_screenshot_on_error():
+            check_capture_fifo(self, cmd=wireshark_k)
 
-    def test_wireshark_capture_from_stdin(self, wireshark_k, check_capture_stdin):
+    def test_wireshark_capture_from_stdin(self, wireshark_k, check_capture_stdin, make_screenshot_on_error):
         '''Capture from stdin using Wireshark'''
-        check_capture_stdin(self, cmd=wireshark_k)
+        with make_screenshot_on_error():
+            check_capture_stdin(self, cmd=wireshark_k)
 
-    def test_wireshark_capture_snapshot_len(self, wireshark_k, check_capture_snapshot_len):
+    def test_wireshark_capture_snapshot_len(self, wireshark_k, check_capture_snapshot_len, make_screenshot_on_error):
         '''Capture truncated packets using Wireshark'''
-        check_capture_snapshot_len(self, cmd=wireshark_k)
+        with make_screenshot_on_error():
+            check_capture_snapshot_len(self, cmd=wireshark_k)
 
 
 @fixtures.mark_usefixtures('test_env')

test/travis-upload-artifacts.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+# Publishes artifacts from a Travis CI build.
+#
+# Copyright (C) 2019 Peter Wu <peter@lekensteyn.nl>
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Currently it dumps a base64-encoded xz-compressed tarball as Travis CI
+# does not have a nice way to publish artifacts (like Gitlab does).
+#
+
+shopt -s nullglob
+files=(*screenshot.png)
+
+if [ ${#files[@]} -eq 0 ]; then
+    echo "No artifacts found"
+    exit
+fi
+
+output=travis.tar.xz
+tar -cJvf "$output" "${files[@]}"
+
+# Print some details for an integrity check.
+ls -l "$output"
+openssl dgst -sha256 "$output"
+
+# Upload to other services just in case the log output is corrupted.
+curl -F 'f:1=<-' ix.io < "$output"
+
+# Dump the contents to the log (note: Travis has a 4MiB limit)
+cat <<EOF
+base64 -d > $output <<ARTIFACTS_BASE64
+$(base64 < "$output" | tr -d '\n' | fold -w200)
+ARTIFACTS_BASE64
+EOF