1 files changed, 54 insertions, 0 deletions
diff --git a/toolkit/components/telemetry/tests/marionette/tests/client/test_main_tab_scalars.py b/toolkit/components/telemetry/tests/marionette/tests/client/test_main_tab_scalars.py
new file mode 100644
index 0000000000..d548d7ccc9
--- /dev/null
+++ b/toolkit/components/telemetry/tests/marionette/tests/client/test_main_tab_scalars.py
@@ -0,0 +1,54 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from telemetry_harness.ping_filters import MAIN_SHUTDOWN_PING
+from telemetry_harness.testcase import TelemetryTestCase
+
+
+class TestMainTabScalars(TelemetryTestCase):
+    """Tests for Telemetry Scalars."""
+
+    def test_main_tab_scalars(self):
+        """Test for Telemetry Scalars."""
+
+        with self.marionette.using_context(self.marionette.CONTEXT_CHROME):
+            # Bug 1829464: BrowserUsageTelemetry's telemetry collection about
+            # open tabs is async. We manually set the task timeout here to 0 ms
+            # so that it instead happens immediately after a tab opens. This
+            # prevents race conditions between telemetry submission and our
+            # test.
+            self.marionette.execute_script(
+                """
+                const { BrowserUsageTelemetry } = ChromeUtils.import(
+                    "resource:///modules/BrowserUsageTelemetry.jsm"
+                );
+
+                BrowserUsageTelemetry._onTabsOpenedTask._timeoutMs = 0;
+                """
+            )
+
+            start_tab = self.marionette.current_window_handle
+
+            tab2 = self.open_tab(focus=True)
+            self.marionette.switch_to_window(tab2)
+
+            tab3 = self.open_tab(focus=True)
+            self.marionette.switch_to_window(tab3)
+
+            self.marionette.close()
+            self.marionette.switch_to_window(tab2)
+
+            self.marionette.close()
+            self.marionette.switch_to_window(start_tab)
+
+        ping = self.wait_for_ping(self.restart_browser, MAIN_SHUTDOWN_PING)
+
+        self.assertEqual(ping["type"], "main")
+        self.assertEqual(ping["clientId"], self.client_id)
+
+        scalars = ping["payload"]["processes"]["parent"]["scalars"]
+
+        self.assertEqual(scalars["browser.engagement.max_concurrent_tab_count"], 3)
+        self.assertEqual(scalars["browser.engagement.tab_open_event_count"], 2)
+        self.assertEqual(scalars["browser.engagement.max_concurrent_window_count"], 1)