diff --git a/packages/backend/test/unit/FetchInstanceMetadataService.ts b/packages/backend/test/unit/FetchInstanceMetadataService.ts
new file mode 100644
index 000000000..1ee293982
--- /dev/null
+++ b/packages/backend/test/unit/FetchInstanceMetadataService.ts
@@ -0,0 +1,109 @@
+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 { FetchInstanceMetadataService } from '@/core/FetchInstanceMetadataService.js';
+import { FederatedInstanceService } from '@/core/FederatedInstanceService.js';
+import { HttpRequestService } from '@/core/HttpRequestService.js';
+import { LoggerService } from '@/core/LoggerService.js';
+import { UtilityService } from '@/core/UtilityService.js';
+import { IdService } from '@/core/IdService.js';
+import { DI } from '@/di-symbols.js';
+import type { TestingModule } from '@nestjs/testing';
+import type { MockFunctionMetadata } from 'jest-mock';
+import { Redis } from 'ioredis'
+
+function mockRedis() {
+	const hash = {};
+	const set = jest.fn((key, value) => {
+			const ret = hash[key];
+			hash[key] = value;
+			return ret;
+		});
+	return set;
+}
+
+describe('FetchInstanceMetadataService', () => {
+	let app: TestingModule;
+	let fetchInstanceMetadataService: jest.Mocked<FetchInstanceMetadataService>;
+	let federatedInstanceService: jest.Mocked<FederatedInstanceService>;
+	let httpRequestService: jest.Mocked<HttpRequestService>;
+	let redisClient: jest.Mocked<Redis.Redis>;
+
+	beforeAll(async () => {
+		app = await Test
+			.createTestingModule({
+				imports: [
+					GlobalModule,
+				],
+				providers: [
+					FetchInstanceMetadataService,
+					LoggerService,
+					UtilityService,
+					IdService,
+				],
+			})
+			.useMocker((token) => {
+				if (token === HttpRequestService) {
+					return { getJson: jest.fn(), getHtml: jest.fn(), send: jest.fn(), };
+				} else if (token === FederatedInstanceService) {
+					return { fetch: jest.fn() };
+				} else if (token === DI.redis) {
+					return mockRedis;
+				}})
+			.compile();
+
+		app.enableShutdownHooks();
+
+		fetchInstanceMetadataService = app.get<FetchInstanceMetadataService>(FetchInstanceMetadataService);
+		federatedInstanceService = app.get<FederatedInstanceService>(FederatedInstanceService) as jest.Mocked<FederatedInstanceService>;
+		redisClient = app.get<Redis.Redis>(DI.redis) as jest.Mocked<Redis.Redis>;
+		httpRequestService = app.get<HttpRequestService>(HttpRequestService) as jest.Mocked<HttpRequestService>;
+	});
+
+	afterAll(async () => {
+		await app.close();
+	});
+
+	test('Lock and update', async () => {
+		redisClient.set = mockRedis();
+		const now = Date.now();
+		federatedInstanceService.fetch.mockReturnValue({ infoUpdatedAt: { getTime: () => { return now - 10 * 1000 * 60 * 60 * 24; } } });
+		httpRequestService.getJson.mockImplementation(() => { throw Error(); });
+		const tryLockSpy = jest.spyOn(fetchInstanceMetadataService, 'tryLock');
+		const unlockSpy = jest.spyOn(fetchInstanceMetadataService, 'unlock');
+		await fetchInstanceMetadataService.fetchInstanceMetadata({ host: "example.com" });
+		expect(tryLockSpy).toHaveBeenCalledTimes(1);
+		expect(unlockSpy).toHaveBeenCalledTimes(1);
+		expect(federatedInstanceService.fetch).toHaveBeenCalledTimes(1);
+		expect(httpRequestService.getJson).toHaveBeenCalled();
+	});
+	test("Lock and don't update", async () => {
+		redisClient.set = mockRedis();
+		const now = Date.now();
+		federatedInstanceService.fetch.mockReturnValue({ infoUpdatedAt: { getTime: () => now } });
+		httpRequestService.getJson.mockImplementation(() => { throw Error(); });
+		const tryLockSpy = jest.spyOn(fetchInstanceMetadataService, 'tryLock');
+		const unlockSpy = jest.spyOn(fetchInstanceMetadataService, 'unlock');
+		await fetchInstanceMetadataService.fetchInstanceMetadata({ host: "example.com" });
+		expect(tryLockSpy).toHaveBeenCalledTimes(1);
+		expect(unlockSpy).toHaveBeenCalledTimes(1);
+		expect(federatedInstanceService.fetch).toHaveBeenCalledTimes(1);
+		expect(httpRequestService.getJson).toHaveBeenCalledTimes(0);
+	});
+	test('Do nothing when lock not acquired', async () => {
+		redisClient.set = mockRedis();
+		federatedInstanceService.fetch.mockReturnValue({ infoUpdatedAt: { getTime: () => now - 10 * 1000 * 60 * 60 * 24 } });
+		httpRequestService.getJson.mockImplementation(() => { throw Error(); });
+		const tryLockSpy = jest.spyOn(fetchInstanceMetadataService, 'tryLock');
+		const unlockSpy = jest.spyOn(fetchInstanceMetadataService, 'unlock');
+		await fetchInstanceMetadataService.tryLock("example.com");
+		await fetchInstanceMetadataService.fetchInstanceMetadata({ host: "example.com" });
+		expect(tryLockSpy).toHaveBeenCalledTimes(2);
+		expect(unlockSpy).toHaveBeenCalledTimes(0);
+		expect(federatedInstanceService.fetch).toHaveBeenCalledTimes(0);
+		expect(httpRequestService.getJson).toHaveBeenCalledTimes(0);
+	});
+});