add test for metaService

packages/backend/test/unit/MetaService.ts

+process.env.NODE_ENV = 'test';
+
+import { jest } from '@jest/globals';
+import { ModuleMocker } from 'jest-mock';
+import { Test } from '@nestjs/testing';
+import { GlobalModule } from '@/GlobalModule.js';
+import type { MetasRepository } from '@/models/index.js';
+import { DI } from '@/di-symbols.js';
+import { MetaService } from '@/core/MetaService.js';
+import { CoreModule } from '@/core/CoreModule.js';
+import type { DataSource } from 'typeorm';
+import type { TestingModule } from '@nestjs/testing';
+import type { MockFunctionMetadata } from 'jest-mock';
+
+const moduleMocker = new ModuleMocker(global);
+
+describe('MetaService', () => {
+	let app: TestingModule;
+	let metaService: MetaService;
+	let metasRepository: MetasRepository;
+
+	beforeAll(async () => {
+		app = await Test.createTestingModule({
+			imports: [
+				GlobalModule,
+				CoreModule,
+			],
+		}).compile();
+
+		app.enableShutdownHooks();
+
+		metaService = app.get<MetaService>(MetaService, { strict: false });
+		metasRepository = app.get<MetasRepository>(DI.metasRepository, { strict: false });
+	});
+
+	afterAll(async () => {
+		await app.close();
+	});
+
+	it('fetch (cache)', async () => {
+		const db = app.get<DataSource>(DI.db);
+		const originalFunction = db.transaction;
+		const spy = jest.spyOn(db, 'transaction');
+		spy.mockImplementation((...args) => originalFunction(...args));
+
+		const result = await metaService.fetch();
+
+		expect(result.id).toBe('x');
+		expect(spy).toHaveBeenCalledTimes(0);
+
+		spy.mockRestore();
+	});
+/*
+	it('fetch (force)', async () => {
+		const db = app.get<DataSource>(DI.db);
+		const originalFunction = db.transaction;
+		const spy = jest.spyOn(db, 'transaction');
+		// 何故かここで無限再帰する db.transaction がspyのままになっている？
+		spy.mockImplementation((...args) => originalFunction(...args));
+
+		const result = await metaService.fetch(true);
+
+		expect(result.id).toBe('x');
+		expect(spy).toHaveBeenCalledTimes(1);
+
+		spy.mockRestore();
+	});*/
+});