Crystal/tests/core.test.ts

import { describe, expect, it, vi } from "vitest";
import "fake-indexeddb/auto";
import { InputController } from "../src/input/controller";
import { CRYSTAL_ROM, validateRom } from "../src/rom/validate";
import {
  BrowserSaveRepository,
  decodeSave,
  encodeSave,
  type SaveRecord,
} from "../src/storage/saves";
import { GameSession } from "../src/app/session";
import type { Emulator } from "../src/emulator/types";

const record: SaveRecord = {
  version: 1,
  romHash: "test-rom",
  coreId: "test-core",
  savedAt: "2026-09-22T12:00:00.000Z",
  state: new Uint8Array([0, 128, 255]),
};

describe("ROM validation", () => {
  it("rejects incorrect sizes without reading the file", async () => {
    const file = new File(["not a game"], "crystal.gbc");
    await expect(validateRom(file)).rejects.toThrow("2 MiB");
  });
  it("rejects a correctly sized file with a forged title and revision", async () => {
    const bytes = new Uint8Array(CRYSTAL_ROM.size);
    bytes.set(new TextEncoder().encode("PM_CRYSTAL"), 0x134);
    bytes[0x14c] = 1;
    await expect(
      validateRom(new File([bytes], "Pokemon Crystal EU 1.1.gbc")),
    ).rejects.toThrow("not a supported English Pokémon Crystal");
  });
});

describe("input aggregation", () => {
  it("keeps a button pressed until all sources release it", () => {
    const send = vi.fn();
    const input = new InputController(send);
    input.press("finger:1", "a");
    input.press("keyboard:x", "a");
    input.release("finger:1");
    expect(send.mock.calls).toEqual([["a", true]]);
    input.release("keyboard:x");
    expect(send.mock.calls).toEqual([
      ["a", true],
      ["a", false],
    ]);
  });
  it("slides a pointer to a different direction and releases everything on interruption", () => {
    const send = vi.fn();
    const input = new InputController(send);
    input.press("finger:1", "up");
    input.press("finger:1", "left");
    expect(send.mock.calls).toEqual([
      ["up", true],
      ["up", false],
      ["left", true],
    ]);
    input.releaseAll();
    expect(input.isPressed("left")).toBe(false);
    expect(send).toHaveBeenCalledWith("left", false);
  });
});

describe("saves", () => {
  it("round trips binary state and rejects incompatible imports", () => {
    const text = encodeSave(record);
    expect(decodeSave(text, record.romHash, record.coreId)).toEqual(record);
    expect(() => decodeSave(text, "another-rom", record.coreId)).toThrow(
      "not compatible",
    );
    expect(() => decodeSave(text, record.romHash, "another-core")).toThrow(
      "not compatible",
    );
    expect(() =>
      decodeSave(
        JSON.stringify({ ...record, state: "???=" }),
        record.romHash,
        record.coreId,
      ),
    ).toThrow("damaged");
  });
  it("persists isolated ROM slots through a fresh repository", async () => {
    const first = new BrowserSaveRepository();
    await first.write(record);
    const second = new BrowserSaveRepository();
    expect(await second.read(record.romHash)).toEqual(record);
    expect(await second.read("another-rom")).toBeUndefined();
  });
});

function setup(saved?: SaveRecord) {
  let bytes = new Uint8Array([3]);
  const emulator: Emulator = {
    id: record.coreId,
    load: vi.fn(async () => {}),
    play: vi.fn(),
    pause: vi.fn(),
    setButton: vi.fn(),
    setMuted: vi.fn(),
    unlockAudio: vi.fn(),
    captureState: () => bytes.slice(),
    restoreState: vi.fn((state) => {
      if (state[0] === 255) throw new Error("Bad state");
      bytes = new Uint8Array(state);
    }),
    exportBattery: () => bytes.slice(),
    dispose: vi.fn(),
  };
  const saves = {
    read: vi.fn(async () => saved),
    write: vi.fn(async (_value: SaveRecord) => {}),
  };
  const session = new GameSession(emulator, saves);
  const rom = {
    bytes: new Uint8Array([1]),
    sha1: record.romHash,
    name: "Synthetic",
  };
  return { emulator, saves, session, rom };
}

describe("session lifecycle", () => {
  it("loads a saved session paused and saves while playing without pausing", async () => {
    const { emulator, saves, session, rom } = setup(record);
    expect(await session.load(rom, {} as HTMLCanvasElement)).toBe(true);
    expect(session.state).toBe("paused");
    expect(emulator.restoreState).toHaveBeenCalledWith(record.state);
    session.play();
    await session.save();
    expect(session.state).toBe("playing");
    expect(saves.write).toHaveBeenCalledOnce();
    session.pause();
    expect(session.state).toBe("paused");
  });
  it("preserves saves from another core and refuses to overwrite them", async () => {
    const { session, rom, saves } = setup({ ...record, coreId: "old" });
    await expect(session.load(rom, {} as HTMLCanvasElement)).rejects.toThrow(
      "migration",
    );
    expect(saves.write).not.toHaveBeenCalled();
    expect(() => session.snapshot()).toThrow("Load a ROM");
  });
  it("rolls back a failed backup import", async () => {
    const { session, rom } = setup();
    await session.load(rom, {} as HTMLCanvasElement);
    await expect(
      session.importSave(
        encodeSave({ ...record, state: new Uint8Array([255]) }),
      ),
    ).rejects.toThrow("Bad state");
    expect(session.snapshot().state).toEqual(new Uint8Array([3]));
  });
  it("reports write failures and allows a later save to succeed", async () => {
    const { session, rom, saves } = setup();
    await session.load(rom, {} as HTMLCanvasElement);
    saves.write.mockRejectedValueOnce(new Error("Quota exceeded"));
    await expect(session.save()).rejects.toThrow("Quota exceeded");
    await expect(session.save()).resolves.toEqual(expect.any(String));
  });
});