为什么运行Rspec时会出现未定义的方法'have'错误？

我最近升级到Rails 4,一切正常,除了我的Rspec测试.

require 'spec_helper'

describe Invoice do

  before :each do
    @user = FactoryGirl.create(:activated_user)
    person = FactoryGirl.create(:person, :user => @user, :company => nil)
    @project = FactoryGirl.create(:project, :user => @user, :person_ids => [person.id], :invoice_recipient_id => person.id)
  end

  it "has a valid factory" do
    expect(FactoryGirl.build(:invoice, :project => @project, :user => @user)).to be_valid
  end

  it "is invalid without a number" do
    expect(FactoryGirl.build(:invoice, :project => @project, :user => @user, :number => nil)).to have(1).errors_on(:number)
  end

end

运行这些测试时,我收到此错误:

Failure/Error: expect(FactoryGirl.build(:invoice, :project => @project, :user => @user, :number => nil)).to have(1).errors_on(:number)
NoMethodError:
undefined method `have' for #
# ./spec/models/invoice_spec.rb:16:in `block (2 levels) in '

谁能告诉我这里缺少什么？

我已经google了,但没有出现.该have方法在Rspec中实际上是相当标准的,我不明白为什么它不应该工作.

谢谢你的任何指示.