test(sample-01): added service unit tests

sample/01-cats-app/src/cats/cats.controller.spec.ts

@@ -31,4 +31,21 @@ describe('CatsController', () => {
       expect(await catsController.findAll()).toBe(result);
     });
   });
+
+  describe('create', () => {
+    it('should add a new cat', async () => {
+      const cat: Cat = {
+        age: 2,
+        breed: 'Bombay',
+        name: 'Pixel',
+      };
+      const expectedCatArray = [cat];
+
+      expect(await catsController.findAll()).toStrictEqual([]);
+
+      await catsController.create(cat);
+
+      expect(await catsController.findAll()).toStrictEqual(expectedCatArray);
+    });
+  });
 });

sample/01-cats-app/src/cats/cats.service.spec.ts

@@ -0,0 +1,46 @@
+import { Test } from '@nestjs/testing';
+import { CatsService } from './cats.service';
+import { Cat } from './interfaces/cat.interface';
+
+describe('CatsService', () => {
+  let catsService: CatsService;
+
+  beforeEach(async () => {
+    const moduleRef = await Test.createTestingModule({
+      providers: [CatsService],
+    }).compile();
+
+    catsService = moduleRef.get<CatsService>(CatsService);
+  });
+
+  describe('findAll', () => {
+    it('should return an array of cats', async () => {
+      const result = [
+        {
+          name: 'Frajola',
+          age: 2,
+          breed: 'Stray',
+        },
+      ];
+      jest.spyOn(catsService, 'findAll').mockImplementation(() => result);
+
+      expect(await catsService.findAll()).toBe(result);
+    });
+  });
+  describe('create', () => {
+    it('should add a new cat', async () => {
+      const cat: Cat = {
+        name: 'Frajola',
+        age: 2,
+        breed: 'Stray',
+      };
+      const expectedCatArray = [cat];
+
+      expect(await catsService.findAll()).toStrictEqual([]);
+
+      await catsService.create(cat);
+
+      expect(await catsService.findAll()).toStrictEqual(expectedCatArray);
+    });
+  });
+});