1 files changed, 74 insertions, 0 deletions
diff --git a/browser/base/content/test/tabs/browser_undo_close_tabs_at_start.js b/browser/base/content/test/tabs/browser_undo_close_tabs_at_start.js
new file mode 100644
index 0000000000..9ad79ea1c8
--- /dev/null
+++ b/browser/base/content/test/tabs/browser_undo_close_tabs_at_start.js
@@ -0,0 +1,74 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const PREF_WARN_ON_CLOSE = "browser.tabs.warnOnCloseOtherTabs";
+
+add_task(async function setPref() {
+  await SpecialPowers.pushPrefEnv({
+    set: [[PREF_WARN_ON_CLOSE, false]],
+  });
+});
+
+add_task(async function replaceEmptyTabs() {
+  const win = await BrowserTestUtils.openNewBrowserWindow();
+  const tabbrowser = win.gBrowser;
+  ok(
+    tabbrowser.tabs.length == 1 && tabbrowser.tabs[0].isEmpty,
+    "One blank tab should be opened."
+  );
+
+  let blankTab = tabbrowser.tabs[0];
+  await BrowserTestUtils.openNewForegroundTab(
+    tabbrowser,
+    "https://example.com/1"
+  );
+  await BrowserTestUtils.openNewForegroundTab(
+    tabbrowser,
+    "https://example.com/2"
+  );
+  await BrowserTestUtils.openNewForegroundTab(
+    tabbrowser,
+    "https://example.com/3"
+  );
+
+  is(tabbrowser.tabs.length, 4, "There should be 4 tabs opened.");
+
+  tabbrowser.removeAllTabsBut(blankTab);
+
+  await TestUtils.waitForCondition(
+    () =>
+      SessionStore.getLastClosedTabCount(win) == 3 &&
+      tabbrowser.tabs.length == 1,
+    "wait for the tabs to close in SessionStore"
+  );
+  is(
+    SessionStore.getLastClosedTabCount(win),
+    3,
+    "SessionStore should know how many tabs were just closed"
+  );
+
+  is(tabbrowser.selectedTab, blankTab, "The blank tab should be selected.");
+
+  win.undoCloseTab();
+
+  await TestUtils.waitForCondition(
+    () => tabbrowser.tabs.length == 3,
+    "wait for the tabs to reopen"
+  );
+
+  is(
+    SessionStore.getLastClosedTabCount(win),
+    SessionStore.getClosedTabCountForWindow(win) ? 1 : 0,
+    "LastClosedTabCount should be reset"
+  );
+
+  ok(
+    !tabbrowser.tabs.includes(blankTab),
+    "The blank tab should have been replaced."
+  );
+
+  // We can't (at the time of writing) check tab order.
+
+  // Cleanup
+  await BrowserTestUtils.closeWindow(win);
+});