2 files changed, 88 insertions, 0 deletions
diff --git a/toolkit/components/aboutwindowsmessages/tests/browser/browser.toml b/toolkit/components/aboutwindowsmessages/tests/browser/browser.toml
new file mode 100644
index 0000000000..650fabf228
--- /dev/null
+++ b/toolkit/components/aboutwindowsmessages/tests/browser/browser.toml
@@ -0,0 +1,3 @@
+[DEFAULT]
+
+["browser_aboutwindowsmessages.js"]
diff --git a/toolkit/components/aboutwindowsmessages/tests/browser/browser_aboutwindowsmessages.js b/toolkit/components/aboutwindowsmessages/tests/browser/browser_aboutwindowsmessages.js
new file mode 100644
index 0000000000..7c667891d6
--- /dev/null
+++ b/toolkit/components/aboutwindowsmessages/tests/browser/browser_aboutwindowsmessages.js
@@ -0,0 +1,85 @@
+/* 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/. */
+
+async function resizeWindow(windowToResize, width, height) {
+  let resizePromise = BrowserTestUtils.waitForEvent(
+    windowToResize,
+    "resize",
+    false
+  );
+  windowToResize.resizeTo(width, height);
+  await resizePromise;
+}
+
+add_task(async () => {
+  const TEST_LINK = "https://example.com/";
+  let originalBrowserWindow =
+    Services.wm.getMostRecentWindow("navigator:browser");
+  let originalBrowser = originalBrowserWindow.gBrowser;
+  // Resize this window so we can check for WM_NCCALCSIZE events below
+  await resizeWindow(originalBrowserWindow, 500, 400);
+  await resizeWindow(originalBrowserWindow, 600, 500);
+  await resizeWindow(originalBrowserWindow, 700, 600);
+  let newWindow = await BrowserTestUtils.openNewBrowserWindow({
+    url: TEST_LINK,
+  });
+  registerCleanupFunction(async function () {
+    await BrowserTestUtils.closeWindow(newWindow);
+  });
+  await BrowserTestUtils.withNewTab(
+    { gBrowser: originalBrowser, url: "about:windows-messages" },
+    async browser => {
+      let messagesList = content.document.getElementById("windows-div");
+      // This is tricky because the test framework has its own windows
+      Assert.greaterOrEqual(
+        messagesList.childNodes.length,
+        2,
+        "should have enough window entries"
+      );
+
+      let firstList = true;
+      for (let sublist of messagesList.childNodes) {
+        const messages = Array.from(sublist.querySelectorAll("li.message"));
+        const numberOfMessages = messages.length;
+        // Every window gets a few window messages when it opens, so there
+        // should be at least a few here.
+        Assert.greaterOrEqual(
+          numberOfMessages,
+          3,
+          "should have enough messages for the current window"
+        );
+        if (firstList) {
+          // It would be nice if we could check for a less obscure event.
+          // However, since we're resizing the window programatically we don't
+          // get WM_SIZE or WM_SIZING events.
+          Assert.greaterOrEqual(
+            messages.filter(messageLi =>
+              messageLi.innerHTML.includes("WM_NCCALCSIZE")
+            ).length,
+            5,
+            "active window should have enough WM_NCCALCSIZE events"
+          );
+          firstList = false;
+        }
+        let buttons = sublist.querySelectorAll("button");
+        Assert.equal(buttons.length, 1, "should have only one button");
+        let clipboardButton = buttons[0];
+        clipboardButton.click();
+        // Wait until copying is done and the button becomes clickable.
+        await BrowserTestUtils.waitForMutationCondition(
+          clipboardButton,
+          { attributes: true },
+          () => !clipboardButton.disabled
+        );
+        const clipboardText = await navigator.clipboard.readText();
+        const numberOfLines = Array.from(clipboardText.matchAll("\n")).length;
+        Assert.equal(
+          numberOfLines,
+          numberOfMessages,
+          "should copy the right number of lines to the clipboard"
+        );
+      }
+    }
+  );
+});