v3: src/ gets one layout rule and keeps to it — each layer holds one kind of module, and every layer is split into the same domains — the previous pass sorted components into folders but left hooks, helpers and a barrel inside them, kept hooks/, utils/ and contexts/ flat, and still grouped most tests by theme. The rule: components/ holds only components (.tsx), contexts/ holds FooContext.ts + FooProvider.tsx pairs, hooks/ every hook, utils/ every non-React module, pages/ one component per route and nothing else. Each of components/, contexts/, hooks/ and utils/ is split into the same domains — auth, category, chat, comment, dump, editor, feed, form, layout, player, playlist, profile, social, theme, ws — plus shared/ for what belongs to no one domain, so the chat is components/chat, contexts/chat, hooks/chat and utils/chat. components/ui becomes components/shared to match. Out of components/: useApiForm goes to hooks/form, chat's message.ts and time.ts to utils/chat (with chatDraft and chatText, now draft.ts and text.ts), the emoji skin tone to utils/editor, the remembered volume to utils/player; player/icons.tsx is PlayerIcons.tsx. components/form/index.ts is gone: everything is imported from its own file, FormProvider straight from react-hook-form, and expectOk sits beside friendlyFetchError in utils/shared/api.ts (apiError.ts), since pages that have no form used it too. Out of pages/: the index's feed views, tab bar and presence row move to components/feed; HotFeed and NewFeed, identical but for the sort, are one DumpFeed with an order prop, which also takes over MainFeedProps from pages/index/types.ts. App is a named export like everything else. Tests mirror the tree one file per module — test/<layer>/<domain>/<Module>.test.tsx — so the themed files (hooks/misc, data, editor, sync; utils/misc, text, storage, remote, journal; contexts/providers; pages/auth and UserSubpages; layout/Fabs) are split by subject, the setup each piece needs kept and the rest dropped; the floating-button test becomes one test per button, 627 tests now. The README states the rule. No behaviour changes; the catalogues only move their source references.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/test/hooks/feed/useFeedCache.test.tsx

@@ -0,0 +1,97 @@
+import { afterEach, describe, expect, test, vi } from "vitest";
+import {
+  act,
+  fireEvent,
+  render,
+  renderHook,
+  screen,
+} from "@testing-library/react";
+import { type ReactNode } from "react";
+import { MemoryRouter, Route, Routes, useNavigate } from "react-router";
+import { useFeedCache } from "../../../hooks/feed/useFeedCache.ts";
+
+afterEach(() => vi.useRealTimers());
+
+describe("useFeedCache", () => {
+  // A MemoryRouter's first entry is a POP, as after Back.
+  const wrapper = () => ({ children }: { children: ReactNode }) => (
+    <MemoryRouter>{children}</MemoryRouter>
+  );
+
+  test("restores a saved feed on a back/forward (POP) visit", () => {
+    const first = renderHook(() => useFeedCache<{ n: number }>("k", (x) => x), {
+      wrapper: wrapper(),
+    });
+    act(() => first.result.current.saveState([{ n: 1 }], 2, true, 300));
+    const second = renderHook(
+      () => useFeedCache<{ n: number }>("k", (x) => ({ n: x.n * 10 })),
+      { wrapper: wrapper() },
+    );
+    expect(second.result.current.cached).toMatchObject({
+      items: [{ n: 10 }],
+      page: 2,
+      hasMore: true,
+      scrollY: 300,
+    });
+  });
+
+  test("an expired entry is ignored", () => {
+    vi.useFakeTimers();
+    const first = renderHook(() => useFeedCache("k", (x) => x), {
+      wrapper: wrapper(),
+    });
+    act(() => first.result.current.saveState([], 1, false, 0));
+    vi.advanceTimersByTime(11 * 60 * 1000);
+    const second = renderHook(() => useFeedCache("k", (x) => x), {
+      wrapper: wrapper(),
+    });
+    expect(second.result.current.cached).toBeNull();
+  });
+
+  test("a fresh (PUSH) visit ignores the cache", () => {
+    sessionStorage.setItem(
+      "k",
+      JSON.stringify({
+        items: [1],
+        page: 1,
+        hasMore: false,
+        scrollY: 0,
+        savedAt: Date.now(),
+      }),
+    );
+    function Probe() {
+      const { cached } = useFeedCache("k", (x) => x);
+      return <p>{cached ? "cached" : "fresh"}</p>;
+    }
+    function Home() {
+      const navigate = useNavigate();
+      return (
+        <button type="button" onClick={() => navigate("/feed")}>
+          go
+        </button>
+      );
+    }
+    render(
+      <MemoryRouter>
+        <Routes>
+          <Route path="/" element={<Home />} />
+          <Route path="/feed" element={<Probe />} />
+        </Routes>
+      </MemoryRouter>,
+    );
+    fireEvent.click(screen.getByText("go"));
+    expect(screen.getByText("fresh")).toBeInTheDocument();
+  });
+
+  test("corrupt storage reads as no cache; a full quota doesn't throw", () => {
+    sessionStorage.setItem("k", "{");
+    const { result } = renderHook(() => useFeedCache("k", (x) => x), {
+      wrapper: wrapper(),
+    });
+    expect(result.current.cached).toBeNull();
+    vi.spyOn(Storage.prototype, "setItem").mockImplementation(() => {
+      throw new Error("QuotaExceededError");
+    });
+    expect(() => result.current.saveState([], 1, false, 0)).not.toThrow();
+  });
+});