1 files changed, 67 insertions, 0 deletions
diff --git a/devtools/client/webconsole/test/browser/browser_console_microtask.js b/devtools/client/webconsole/test/browser/browser_console_microtask.js
new file mode 100644
index 0000000000..5f6103c678
--- /dev/null
+++ b/devtools/client/webconsole/test/browser/browser_console_microtask.js
@@ -0,0 +1,67 @@
+/* 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/. */
+
+// The console input should be evaluated with microtask level != 0.
+
+"use strict";
+
+add_task(async function () {
+  // Needed for the execute() function below
+  await pushPref("security.allow_parent_unrestricted_js_loads", true);
+
+  const hud = await BrowserConsoleManager.toggleBrowserConsole();
+
+  hud.iframeWindow.focus();
+  execute(
+    hud,
+    `
+{
+  let logCount = 0;
+
+  queueMicrotask(() => {
+    console.log("#" + logCount + ": in microtask");
+    logCount++;
+  });
+
+  console.log("#" + logCount + ": before createXULElement");
+  logCount++;
+
+  // This shouldn't perform microtask checkpoint.
+  document.createXULElement("browser");
+
+  console.log("#" + logCount + ": after createXULElement");
+  logCount++;
+}
+`
+  );
+
+  const beforeCreateXUL = await waitFor(() =>
+    findConsoleAPIMessage(hud, "before createXULElement")
+  );
+  const afterCreateXUL = await waitFor(() =>
+    findConsoleAPIMessage(hud, "after createXULElement")
+  );
+  const inMicroTask = await waitFor(() =>
+    findConsoleAPIMessage(hud, "in microtask")
+  );
+
+  const getMessageIndex = msg => {
+    const text = msg.textContent;
+    return text.match(/^#(\d+)/)[1];
+  };
+
+  is(
+    getMessageIndex(beforeCreateXUL),
+    "0",
+    "before createXULElement log is displayed first"
+  );
+  is(
+    getMessageIndex(afterCreateXUL),
+    "1",
+    "after createXULElement log is displayed second"
+  );
+  is(getMessageIndex(inMicroTask), "2", "in microtask log is displayed last");
+
+  ok(true, "Expected messages are displayed in the browser console");
+});