1 files changed, 53 insertions, 0 deletions
diff --git a/browser/components/sessionstore/test/browser_switch_remoteness.js b/browser/components/sessionstore/test/browser_switch_remoteness.js
new file mode 100644
index 0000000000..daea961335
--- /dev/null
+++ b/browser/components/sessionstore/test/browser_switch_remoteness.js
@@ -0,0 +1,53 @@
+"use strict";
+
+const URL = "http://example.com/browser_switch_remoteness_";
+
+function countHistoryEntries(browser, expected) {
+  return SpecialPowers.spawn(browser, [{ expected }], async function (args) {
+    let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
+    let history = webNavigation.sessionHistory;
+    Assert.equal(
+      history && history.count,
+      args.expected,
+      "correct number of shistory entries"
+    );
+  });
+}
+
+add_task(async function () {
+  // Open a new window.
+  let win = await promiseNewWindowLoaded();
+
+  // Add a new tab.
+  let tab = BrowserTestUtils.addTab(win.gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+  ok(browser.isRemoteBrowser, "browser is remote");
+
+  // Get the maximum number of preceding entries to save.
+  const MAX_BACK = Services.prefs.getIntPref(
+    "browser.sessionstore.max_serialize_back"
+  );
+  ok(MAX_BACK > -1, "check that the default has a value that caps data");
+
+  // Load more pages than we would save to disk on a clean shutdown.
+  for (let i = 0; i < MAX_BACK + 2; i++) {
+    BrowserTestUtils.loadURIString(browser, URL + i);
+    await promiseBrowserLoaded(browser);
+    ok(browser.isRemoteBrowser, "browser is still remote");
+  }
+
+  // Check we have the right number of shistory entries.
+  await countHistoryEntries(browser, MAX_BACK + 2);
+
+  // Load a non-remote page.
+  BrowserTestUtils.loadURIString(browser, "about:robots");
+  await promiseBrowserLoaded(browser);
+  ok(!browser.isRemoteBrowser, "browser is not remote anymore");
+
+  // Check that we didn't lose any shistory entries.
+  await countHistoryEntries(browser, MAX_BACK + 3);
+
+  // Cleanup.
+  await BrowserTestUtils.closeWindow(win);
+});