我有一个用户模型和一个项目模型。
用户可以创建多个项目，而一个项目只有一个所有者，可以有多个成员。

# app/models/user.rb

class User < ApplicationRecord
    has_secure_password
    has_many :projects
    has_and_belongs_to_many :projects
end

# app/models/project.rb

class Project < ApplicationRecord
    belongs_to :user
    has_and_belongs_to_many :users
end

这将创建一个数据库表，如下所示：

create_table "projects", force: :cascade do |t|
    t.string "name"
    t.integer "user_id" #id of the owner of the projects
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["user_id"], name: "index_projects_on_user_id"
  end

  create_table "projects_users", force: :cascade do |t|
    t.integer "user_id" #id of the member of the project
    t.integer "project_id" #project that the member joined
    t.index ["project_id"], name: "index_projects_users_on_project_id"
    t.index ["user_id"], name: "index_projects_users_on_user_id"
  end

  create_table "users", force: :cascade do |t|
    t.string "first_name"
    t.string "last_name"
    t.string "email"
    t.string "password_digest"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

其中，projects_users表是为has_and_belongs_to_many关联创建的连接点/网桥表。
但是，每当我使用rspec运行测试时，应该只有一个成功，另一个失败，因为在user.rb文件中，:projects定义了两次。

# spec/models/user_spec.rb

require 'rails_helper'
RSpec.describe User, :type => :model do
      context 'associations' do
        it { should have_many(:projects) } #error
        it { should have_and_belong_to_many(:projects) } #success
      end
    end

错误为Failure/Error: it { should have_many(:projects) } Expected User to have a has_many association called projects (actual association type was has_and_belongs_to_many)

# spec/models/project_spec.rb

require 'rails_helper'

RSpec.describe Project, :type => :model do
  context 'associations' do
    it { should belong_to(:user) } #success
    it { should have_and_belong_to_many(:users) } #success
  end
end

如何在一个模型中正确测试多个关联？