JEST: Add Jest test to test migration from v2 to v3 (#2305)

test/jest/Migration/Migration.test.ts

@@ -0,0 +1,40 @@
+import { Player } from "@player";
+import fs from "node:fs";
+import type { ScriptFilePath } from "../../../src/Paths/ScriptFilePath";
+import { loadGame } from "../../../src/SaveObject";
+import * as db from "../../../src/db";
+import * as FileUtils from "../../../src/utils/FileUtils";
+
+describe("v3", () => {
+  test("v2.8.1 to v3.0.0", async () => {
+    const saveData = new Uint8Array(fs.readFileSync("test/jest/Migration/save-files/v2.8.1.gz"));
+
+    // Simulate loading the data in IndexedDB
+    const mockedLoad = jest.spyOn(db, "load");
+    /**
+     * We must use structuredClone(saveData) instead of saveData; otherwise, the check of mockedDownload won't catch
+     * wrong changes in evaluateVersionCompatibility (e.g., unexpectedly mutating saveData before passing it to
+     * downloadContentAsFile).
+     */
+    mockedLoad.mockReturnValue(Promise.resolve(structuredClone(saveData)));
+
+    const mockedDownload = jest.spyOn(FileUtils, "downloadContentAsFile");
+
+    await loadGame(await db.load());
+
+    // Check if auto-migration works
+    expect(
+      Player.getHomeComputer()
+        .scripts.get("a.js" as ScriptFilePath)
+        ?.code.includes("ns.ui.openTail()"),
+    ).toStrictEqual(true);
+    if (!Player.corporation) {
+      throw new Error("The save file does not have corporation data");
+    }
+    expect(Object.keys(Player.corporation.upgrades).includes("DreamSense")).toStrictEqual(false);
+    expect(Player.corporation.funds).toStrictEqual(110e9);
+
+    // Check if evaluateVersionCompatibility correctly loads the data in IndexedDB and passes it to downloadContentAsFile
+    expect(mockedDownload).toHaveBeenCalledWith(saveData, "bitburnerSave_backup_2.8.1_1756913326.json.gz");
+  });
+});