RSpec：未定义的方法`assert_difference'for ...（NoMethodError）

Question

context 'with event_type is available create event' do 
    let(:event_type) { EventType.where(name: 'visit_site').first } 
    assert_difference 'Event.count' do 
    Event.fire_event(event_type, @sponge,{}) 
    end 
end 

我搜索了Google的这个错误，但没有找到解决的办法。 请帮助我。谢谢:)

Answer 1

请务必包括AssertDifference在投机/ spec_helper.rb：

RSpec.configure do |config| 
    ... 
    config.include AssertDifference 
end 

并把断言的it块内：

it 'event count should change' do 
    assert_difference 'Event.count' do 
    ... 
    end 
end 

Answer 2

我最好重写使用change。

这确实在RSpec 3.x中有效，但可能在旧版本中也是如此。

context 'with event_type is available create event' do 
    let(:event_type) { EventType.where(name: 'visit_site').first } 

    it "changes event counter" do 
    expect { Event.fire_event(event_type, @sponge,{}) }.to change { Event.count } 
    end 
end # with event_type is available create event 

Answer 3

如果您使用的是RSPEC，肯定应该是“改变”的方法。这里有两个例子消极和积极的一个，这样你可以有语法感：

RSpec.describe "UsersSignups", type: :request do 
    describe "signing up with invalid information" do 
    it "should not work and should go back to the signup form" do 
     get signup_path 
     expect do 
     post users_path, user: { 
      first_name:   "", 
      last_name:    "miki", 
      email:     "user@triculi", 
      password:    "buajaja", 
      password_confirmation: "juababa" 
     } 
     end.to_not change{ User.count } 
     expect(response).to render_template(:new) 
     expect(response.body).to include('errors') 
    end 
    end 

    describe "signing up with valid information" do 
    it "should work and should redirect to user's show view" do 
     get signup_path 
     expect do 
     post_via_redirect users_path, user: { 
      first_name:   "Julito", 
      last_name:    "Triculi", 
      email:     "triculito@mail.com", 
      password:    "worldtriculi", 
      password_confirmation: "worldtriculi" 
     } 
     end.to change{ User.count }.from(0).to(1) 
     expect(response).to render_template(:show) 
     expect(flash[:success]).to_not be(nil) 
    end 
    end