feat: ✨ add user resolver

apps/users-application/src/users/users.resolver.spec.ts

@@ -0,0 +1,64 @@
+import { Test, TestingModule } from '@nestjs/testing';
+import { UsersResolver } from './users.resolver';
+import { UsersService } from './users.service';
+import { User } from './models/user.model';
+
+describe('UsersResolver', () => {
+  let resolver: UsersResolver;
+  let service: UsersService;
+
+  beforeEach(async () => {
+    const module: TestingModule = await Test.createTestingModule({
+      providers: [
+        UsersResolver,
+        {
+          provide: UsersService,
+          useValue: {
+            findById: jest.fn(),
+          },
+        },
+      ],
+    }).compile();
+
+    resolver = module.get<UsersResolver>(UsersResolver);
+    service = module.get<UsersService>(UsersService);
+  });
+
+  it('should be defined', () => {
+    expect(resolver).toBeDefined();
+  });
+
+  describe('getUser', () => {
+    it('should return a user by id', () => {
+      const user: User = { id: 1, name: 'John Doe' };
+      jest.spyOn(service, 'findById').mockReturnValue(user);
+
+      expect(resolver.getUser(1)).toEqual(user);
+      expect(service.findById).toHaveBeenCalledWith(1);
+    });
+
+    it('should return undefined if user not found', () => {
+      jest.spyOn(service, 'findById').mockReturnValue(undefined);
+
+      expect(resolver.getUser(1)).toBeUndefined();
+      expect(service.findById).toHaveBeenCalledWith(1);
+    });
+  });
+
+  describe('resolveReference', () => {
+    it('should return a user by reference id', () => {
+      const user: User = { id: 1, name: 'John Doe' };
+      jest.spyOn(service, 'findById').mockReturnValue(user);
+
+      expect(resolver.resolveReference({ __typename: 'User', id: 1 })).toEqual(user);
+      expect(service.findById).toHaveBeenCalledWith(1);
+    });
+
+    it('should return undefined if user not found by reference id', () => {
+      jest.spyOn(service, 'findById').mockReturnValue(undefined);
+
+      expect(resolver.resolveReference({ __typename: 'User', id: 1 })).toBeUndefined();
+      expect(service.findById).toHaveBeenCalledWith(1);
+    });
+  });
+});

apps/users-application/src/users/users.resolver.ts

@@ -0,0 +1,22 @@
+import { Args, ID, Query, Resolver, ResolveReference } from '@nestjs/graphql';
+
+import { User } from './models/user.model';
+import { UsersService } from './users.service';
+
+@Resolver(() => User)
+export class UsersResolver {
+  constructor(private usersService: UsersService) {}
+
+  @Query()
+  getUser(@Args({ name: 'id', type: () => ID }) id: number): User | undefined {
+    return this.usersService.findById(id);
+  }
+
+  @ResolveReference()
+  resolveReference(reference: {
+    __typename: string;
+    id: number;
+  }): User | undefined {
+    return this.usersService.findById(reference.id);
+  }
+}