test: added tests for caching service

src/caching/services/cache.service.spec.ts

@@ -0,0 +1,60 @@
+import { Test, TestingModule } from '@nestjs/testing';
+import { Logger } from '@nestjs/common';
+import { CACHE_MANAGER } from '@nestjs/cache-manager';
+import { CachingService } from './cache.service';
+
+describe('CacheService', () => {
+  let service: CachingService;
+  const mockCacheManager = {
+    get: jest.fn(),
+    set: jest.fn(),
+  };
+
+  beforeEach(async () => {
+    const module: TestingModule = await Test.createTestingModule({
+      providers: [
+        CachingService,
+        Logger,
+        { provide: CACHE_MANAGER, useValue: mockCacheManager },
+      ],
+    }).compile();
+
+    service = module.get<CachingService>(CachingService);
+  });
+
+  afterEach(() => {
+    jest.resetAllMocks();
+    jest.clearAllMocks();
+  });
+
+  it('should be defined', () => {
+    expect(service).toBeDefined();
+  });
+
+  it('should save the result to the cache', async () => {
+    await service.store('foo', 'bar');
+    expect(mockCacheManager.set).toBeCalledTimes(1);
+  });
+
+  it('should not throw an error whenever something went wrong while saving the result to the cache', async () => {
+    jest.spyOn(mockCacheManager, 'set').mockImplementationOnce(() => {
+      throw Error('No way!');
+    });
+    await service.store('foo', 'bar');
+    expect(mockCacheManager.set).toBeCalledTimes(1);
+  });
+
+  it('should check the result to the cache', async () => {
+    jest.spyOn(mockCacheManager, 'get').mockResolvedValue('bar');
+    expect(await service.checkCache('foo')).toEqual('bar');
+    expect(mockCacheManager.get).toBeCalledTimes(1);
+  });
+
+  it('should return undefined whenever an error occurred during cache lookup', async () => {
+    jest.spyOn(mockCacheManager, 'get').mockImplementationOnce(() => {
+      throw Error('No way!');
+    });
+    expect(await service.checkCache('foo')).toEqual(undefined);
+    expect(mockCacheManager.get).toBeCalledTimes(1);
+  });
+});