user.builder.js

export class UserBuilder {
  constructor() {
    this.user = {
      name: '',
      avatar: '',
      // etc
    };
  }
  
  stub() {
    this.user.name = 'Bob';
    this.user.avatar = 'http://yesss.com';
    this.user.role = 'user';
    
    return this;
  }
  
  withName(name) {
    this.user.name = name;
    return this;
  }
  
  withAvatar(avatar) {
    this.user.avatar = avatar;
    return this;
  }
  
  asUser() {
    this.user.role = 'user';
    return this;
  }
  
  asAdmin() {
    this.user.role = 'admin';
    return this;
  }
  
  build() {
    return {...this.user}
  }
}

// Usage:
const mockUser = new UserBuilder().stub().asAdmin().build();