test(nav): pin the restore's last look and the clearing of the name it looks for

frontend/src/lib/listNav.restoreMoved.dom.test.tsx

@@ -13,6 +13,7 @@ import {
   NAV_REVEAL_EVENT,
   navItemAttrs,
   navPosition,
+  pendingNavName,
   restoreNavPosition,
   useListNav,
 } from "./listNav";
@@ -150,4 +151,56 @@ describe("Back to an item that moved to another list", () => {
       document.querySelector("main")!.firstElementChild,
     );
   });
+
+  it("looks in another list at its last look when its own never renders the place it counts", async () => {
+    vi.useFakeTimers();
+    try {
+      const { unmount } = render(<Page lists={[["older", "subscribed"], ["subscribed-2"]]} />);
+      button("subscribed").focus();
+      const pos = navPosition()!;
+      unmount();
+      // Its own list still counts two, and keeps showing one; the item is in the next list.
+      render(<Page lists={[["older"], ["subscribed"]]} counts={[2]} />);
+      const cancel = restoreNavPosition(pos);
+      await act(async () => vi.advanceTimersByTimeAsync(1000));
+      expect(focused()).toBeUndefined(); // still giving its own list the chance
+      await act(async () => vi.advanceTimersByTimeAsync(1100));
+      expect(focused()).toBe("subscribed");
+      cancel();
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+});
+
+describe("the name a Back is still looking for", () => {
+  const pos = { list: 0, lists: 1, index: 0, name: "subscribed" };
+
+  it("is there while it looks, and gone once cancelled", () => {
+    const cancel = restoreNavPosition(pos);
+    expect(pendingNavName()).toBe("subscribed");
+    cancel();
+    expect(pendingNavName()).toBeNull();
+  });
+
+  it("is gone once the focus went somewhere else", async () => {
+    render(<button>elsewhere</button>);
+    const cancel = restoreNavPosition(pos);
+    button("elsewhere").focus();
+    await wait(80);
+    expect(pendingNavName()).toBeNull();
+    cancel();
+  });
+
+  it("is gone once it gave up", async () => {
+    vi.useFakeTimers();
+    try {
+      const cancel = restoreNavPosition(pos);
+      await vi.advanceTimersByTimeAsync(2100);
+      expect(pendingNavName()).toBeNull();
+      cancel();
+    } finally {
+      vi.useRealTimers();
+    }
+  });
 });