1 files changed, 56 insertions, 0 deletions
diff --git a/devtools/client/inspector/grids/test/browser_grids_number-of-css-grids-telemetry.js b/devtools/client/inspector/grids/test/browser_grids_number-of-css-grids-telemetry.js
new file mode 100644
index 0000000000..6ec6b32a63
--- /dev/null
+++ b/devtools/client/inspector/grids/test/browser_grids_number-of-css-grids-telemetry.js
@@ -0,0 +1,56 @@
+/* Any copyright is dedicated to the Public Domain.
+ http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Tests that the telemetry count for the number of CSS Grid Elements on a page navigation
+// is correct when the toolbox is opened.
+
+const TEST_URI1 = `
+  <div></div>
+`;
+
+const TEST_URI2 = `
+  <style type='text/css'>
+    #grid {
+      display: grid;
+    }
+  </style>
+  <div id="grid">
+    <div id="cell1">cell1</div>
+    <div id="cell2">cell2</div>
+  </div>
+`;
+
+add_task(async function () {
+  await addTab("data:text/html;charset=utf-8," + encodeURIComponent(TEST_URI1));
+
+  startTelemetry();
+
+  const { inspector } = await openLayoutView();
+  const { store } = inspector;
+
+  info("Navigate to TEST_URI2");
+
+  const onGridListUpdate = waitUntilState(
+    store,
+    state => state.grids.length == 1
+  );
+  await navigateTo(
+    "data:text/html;charset=utf-8," + encodeURIComponent(TEST_URI2)
+  );
+  await onGridListUpdate;
+
+  checkResults();
+});
+
+function checkResults() {
+  // Check for:
+  //   - 1 CSS Grid Element
+  checkTelemetry(
+    "DEVTOOLS_NUMBER_OF_CSS_GRIDS_IN_A_PAGE",
+    "",
+    { 0: 0, 1: 1, 2: 0 },
+    "array"
+  );
+}