add: i18n backend support

the backend is being supported by using msw which will import the correct file from the local locales folder

global.d.ts

@@ -0,0 +1,14 @@
+import type { SetupServerApi } from "msw/node";
+
+export {};
+
+declare global {
+  /**
+   * Only used in testing.
+   * Can technically be undefined/null but for ease of use we are going to assume it is always defined.
+   * Used to looad i18n files exclusively.
+   * 
+   * To set up your own server in a test see `game_data.test.ts`
+   */
+  var i18nServer: SetupServerApi;
+}

src/test/vitest.setup.ts

@@ -4,16 +4,17 @@ import { initLoggedInUser } from "#app/account";
 import { initAbilities } from "#app/data/ability";
 import { initBiomes } from "#app/data/balance/biomes";
 import { initEggMoves } from "#app/data/balance/egg-moves";
+import { initPokemonPrevolutions } from "#app/data/balance/pokemon-evolutions";
 import { initMoves } from "#app/data/move";
 import { initMysteryEncounters } from "#app/data/mystery-encounters/mystery-encounters";
-import { initPokemonPrevolutions } from "#app/data/balance/pokemon-evolutions";
 import { initPokemonForms } from "#app/data/pokemon-forms";
 import { initSpecies } from "#app/data/pokemon-species";
 import { initAchievements } from "#app/system/achv";
 import { initVouchers } from "#app/system/voucher";
 import { initStatsKeys } from "#app/ui/game-stats-ui-handler";
-import { beforeAll, vi } from "vitest";
+import { afterAll, beforeAll, vi } from "vitest";
 
+/** Set the timezone to UTC for tests. */
 process.env.TZ = "UTC";
 
 /** Mock the override import to always return default values, ignoring any custom overrides. */
@@ -26,26 +27,36 @@ vi.mock("#app/overrides", async (importOriginal) => {
   } satisfies typeof import("#app/overrides");
 });
 
-vi.mock("i18next", () => ({
-  default: {
-    use: () => {},
-    t: (key: string) => key,
-    changeLanguage: () => Promise.resolve(),
-    init: () => Promise.resolve(),
-    resolvedLanguage: "en",
-    exists: () => true,
-    getDataByLanguage:() => ({
-      en: {
-        keys: ["foo"]
-      },
-    }),
-    services: {
-      formatter: {
-        add: () => {},
+/**
+ * This is a hacky way to mock the i18n backend requests (with the help of {@link https://mswjs.io/ | msw}).
+ * The reason to put it inside of a mock is to elevate it.
+ * This is necessary because how our code is structured.
+ * Do NOT try to put any of this code into external functions, it won't work as it's elevated during runtime.
+ */
+vi.mock("i18next", async (importOriginal) => {
+  console.log("Mocking i18next");
+  const { setupServer } = await import("msw/node");
+  const { http, HttpResponse } = await import("msw");
+
+  global.i18nServer = setupServer(
+    http.get("/locales/en/*", async (req) => {
+      const filename = req.params[0];
+
+      try {
+        const json = await import(`../../public/locales/en/${req.params[0]}`);
+        console.log("Loaded locale", filename);
+        return HttpResponse.json(json);
+      } catch (err) {
+        console.log(`Failed to load locale ${filename}!`, err);
+        return HttpResponse.json({});
       }
-    },
-  },
-}));
+    })
+  );
+  global.i18nServer.listen({ onUnhandledRequest: "error" });
+  console.log("i18n MSW server listening!");
+
+  return await importOriginal();
+});
 
 initVouchers();
 initAchievements();
@@ -70,3 +81,8 @@ beforeAll(() => {
     },
   });
 });
+
+afterAll(() => {
+  global.i18nServer.close();
+  console.log("Closing i18n MSW server!");
+});