生成服务，demo，nest generate service demo posts/providers

src/app.module.ts

@@ -2,10 +2,11 @@ import { Module } from '@nestjs/common';
 import { AppController } from './app.controller';
 import { AppService } from './app.service';
 import { PostsController } from './posts/posts.controller';
+import { DemoService } from './posts/providers/demo/demo.service';
 
 @Module({
   imports: [],
   controllers: [AppController, PostsController],
-  providers: [AppService],
+  providers: [AppService, DemoService],
 })
 export class AppModule {}

src/posts/providers/demo/demo.service.spec.ts

@@ -0,0 +1,18 @@
+import { Test, TestingModule } from '@nestjs/testing';
+import { DemoService } from './demo.service';
+
+describe('DemoService', () => {
+  let service: DemoService;
+
+  beforeEach(async () => {
+    const module: TestingModule = await Test.createTestingModule({
+      providers: [DemoService],
+    }).compile();
+
+    service = module.get<DemoService>(DemoService);
+  });
+
+  it('should be defined', () => {
+    expect(service).toBeDefined();
+  });
+});

src/posts/providers/demo/demo.service.ts

@@ -0,0 +1,4 @@
+import { Injectable } from '@nestjs/common';
+
+@Injectable()
+export class DemoService {}