1 files changed, 47 insertions, 0 deletions
diff --git a/devtools/client/inspector/flexbox/test/browser_flexbox_item_list_updates_on_change.js b/devtools/client/inspector/flexbox/test/browser_flexbox_item_list_updates_on_change.js
new file mode 100644
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--- /dev/null
+++ b/devtools/client/inspector/flexbox/test/browser_flexbox_item_list_updates_on_change.js
@@ -0,0 +1,47 @@
+/* Any copyright is dedicated to the Public Domain.
+ http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Test that the flex item list updates on changes to the number of flex items in the
+// flex container.
+
+const TEST_URI = `
+  <style>
+    #container {
+      display: flex;
+    }
+  </style>
+  <div id="container">
+    <div></div>
+  </div>
+`;
+
+add_task(async function () {
+  await addTab("data:text/html;charset=utf-8," + encodeURIComponent(TEST_URI));
+  const { inspector, flexboxInspector } = await openLayoutView();
+  const { document: doc } = flexboxInspector;
+
+  const onFlexItemListRendered = waitForDOM(doc, ".flex-item-list");
+  await selectNode("#container", inspector);
+  const [flexItemList] = await onFlexItemListRendered;
+
+  info("Checking the initial state of the flex item list.");
+  ok(flexItemList, "The flex item list is rendered.");
+  is(
+    flexItemList.querySelectorAll("button").length,
+    1,
+    "Got the correct number of flex items in the list."
+  );
+
+  info("Changing the flexbox in the page.");
+  const onFlexItemListChanged = waitForDOM(doc, ".flex-item-list > button", 2);
+  await SpecialPowers.spawn(gBrowser.selectedBrowser, [], () => {
+    const div = content.document.createElement("div");
+    content.document.getElementById("container").appendChild(div);
+  });
+  const elements = await onFlexItemListChanged;
+
+  info("Checking the flex item list is correct.");
+  is(elements.length, 2, "Flex item list was changed.");
+});