1 files changed, 109 insertions, 0 deletions
diff --git a/browser/components/sessionstore/test/browser_closedId.js b/browser/components/sessionstore/test/browser_closedId.js
new file mode 100644
index 0000000000..6e5c9d7543
--- /dev/null
+++ b/browser/components/sessionstore/test/browser_closedId.js
@@ -0,0 +1,109 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const BACKUP_STATE = SessionStore.getBrowserState();
+
+async function add_new_tab(URL) {
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+  return tab;
+}
+
+add_task(async function test_closedId_order() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.sessionstore.restore_on_demand", true],
+      ["browser.sessionstore.restore_tabs_lazily", true],
+    ],
+  });
+  // reset to 0
+  SessionStore.resetNextClosedId();
+  await promiseBrowserState({
+    windows: [
+      {
+        selected: 1, // SessionStore uses 1-based indexing.
+        tabs: [
+          {
+            entries: [],
+          },
+        ],
+        _closedTabs: [
+          {
+            state: {
+              entries: [
+                {
+                  url: "https://www.example.com/",
+                  triggeringPrincipal_base64,
+                },
+              ],
+              selected: 1,
+            },
+            closedId: 0,
+            closedAt: Date.now() - 100,
+            title: "Example",
+          },
+          {
+            state: {
+              entries: [
+                {
+                  url: "about:mozilla",
+                  triggeringPrincipal_base64,
+                },
+              ],
+            },
+            closedId: 1,
+            closedAt: Date.now() - 50,
+            title: "about:mozilla",
+          },
+          {
+            state: {
+              entries: [
+                {
+                  url: "https://www.example.net/",
+                  triggeringPrincipal_base64,
+                },
+              ],
+            },
+            closedId: 2,
+            closedAt: Date.now(),
+            title: "Example",
+          },
+        ],
+      },
+    ],
+  });
+
+  let tab = await add_new_tab("about:firefoxview");
+
+  is(
+    SessionStore.getClosedTabCountForWindow(window),
+    3,
+    "Closed tab count after restored session is 3"
+  );
+
+  let initialClosedId =
+    SessionStore.getClosedTabDataForWindow(window)[0].closedId;
+
+  // If this fails, that means one of the closedId's in the stubbed data in this test needs to be updated
+  // to reflect what the initial closedId is when a new tab is open and closed (which may change as more tests
+  // for session store are added here). You can manually verify a change to stubbed data by commenting out
+  // this._resetClosedIds in SessionStore.sys.mjs temporarily and then the "Each tab has a unique closedId" case should fail.
+  is(initialClosedId, 0, "Initial closedId is 0");
+
+  await openAndCloseTab(window, "about:robots"); // closedId should be higher than the ones we just restored.
+
+  let closedData = SessionStore.getClosedTabDataForWindow(window);
+  is(closedData.length, 4, "Should have data for 4 closed tabs.");
+  is(
+    new Set(closedData.map(t => t.closedId)).size,
+    4,
+    "Each tab has a unique closedId"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+
+  // Clean up for the next task.
+  await promiseBrowserState(BACKUP_STATE);
+});