MOBILE-3833 behat: Document performance config

tests/behat/classes/performance_measure.php

@@ -14,6 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
+use Behat\Mink\Exception\DriverException;
+use Facebook\WebDriver\Exception\InvalidArgumentException;
 use Moodle\BehatExtension\Driver\WebDriver;
 
 /**
@@ -268,7 +270,7 @@ class performance_measure implements behat_app_listener {
         $scripting = 0;
         $styling = 0;
         $networking = 0;
-        $logs = $this->driver->getWebDriver()->manage()->getLog('performance');
+        $logs = $this->getPerformanceLogs();
 
         foreach ($logs as $log) {
             // TODO this should filter by end time as well, but it seems like the timestamps are not
@@ -304,4 +306,39 @@ class performance_measure implements behat_app_listener {
         $this->networking = $networking;
     }
 
+    /**
+     * Get performance logs.
+     *
+     * @return array Performance logs.
+     */
+    private function getPerformanceLogs(): array {
+        try {
+            return $this->driver->getWebDriver()->manage()->getLog('performance');
+        } catch (InvalidArgumentException $e) {
+            throw new DriverException(
+                implode("\n", [
+                    "It wasn't possible to get performance logs, make sure that you have configured the following capabilities:",
+                    "",
+                    "\$CFG->behat_profiles = [",
+                    "    'default' => [",
+                    "        'browser' => 'chrome',",
+                    "        'wd_host' => 'http://selenium:4444/wd/hub',",
+                    "        'capabilities' => [",
+                    "            'extra_capabilities' => [",
+                    "                'goog:loggingPrefs' => ['performance' => 'ALL'],",
+                    "                'chromeOptions' => [",
+                    "                    'perfLoggingPrefs' => [",
+                    "                        'traceCategories' => 'devtools.timeline',",
+                    "                    ],",
+                    "                ],",
+                    "            ],",
+                    "        ],",
+                    "    ],",
+                    ");",
+                    "",
+                ])
+            );
+        }
+    }
+
 }

tests/behat/performance.feature

@@ -1,6 +1,25 @@
 @app @javascript @performance
 Feature: Measure performance.
 
+  # In order to run performance tests, you need to add the following capabilities to your Behat configuration:
+  #
+  # $CFG->behat_profiles = [
+  #     'default' => [
+  #         'browser' => 'chrome',
+  #         'wd_host' => 'http://selenium:4444/wd/hub',
+  #         'capabilities' => [
+  #             'extra_capabilities' => [
+  #                 'goog:loggingPrefs' => ['performance' => 'ALL'],
+  #                 'chromeOptions' => [
+  #                     'perfLoggingPrefs' => [
+  #                         'traceCategories' => 'devtools.timeline',
+  #                     ],
+  #                 ],
+  #             ],
+  #         ],
+  #     ],
+  # ];
+
   Background:
     Given the following "users" exist:
       | username |