1 files changed, 38 insertions, 0 deletions
diff --git a/comm/mail/components/extensions/test/browser/browser_ext_messageDisplay_bug1827032.js b/comm/mail/components/extensions/test/browser/browser_ext_messageDisplay_bug1827032.js
new file mode 100644
index 0000000000..ebae544585
--- /dev/null
+++ b/comm/mail/components/extensions/test/browser/browser_ext_messageDisplay_bug1827032.js
@@ -0,0 +1,38 @@
+/* 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/. */
+
+/**
+ * Test to make sure messageDisplay.getDisplayedMessage() returns null for
+ * non-message tabs.
+ */
+add_task(async function testGetDisplayedMessageInComposeTab() {
+  let files = {
+    "background.js": async () => {
+      let composeTab = await browser.compose.beginNew();
+      browser.test.assertEq(
+        composeTab.type,
+        "messageCompose",
+        "Should have found a compose tab"
+      );
+
+      let msg = await browser.messageDisplay.getDisplayedMessage(composeTab.id);
+      browser.test.assertTrue(!msg, "Should not have found a message");
+
+      await browser.tabs.remove(composeTab.id);
+      browser.test.notifyPass("finished");
+    },
+    "utils.js": await getUtilsJS(),
+  };
+  let extension = ExtensionTestUtils.loadExtension({
+    files,
+    manifest: {
+      background: { scripts: ["utils.js", "background.js"] },
+      permissions: ["compose", "messagesRead"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("finished");
+  await extension.unload();
+});