Rspecでrake taskをテストする方法

ほとんど定型文です。理解しないでもかけます。

lib/tasks/sample.rake

task sample: :environment do
  user = User.first
  user.destroy!
end

spec/lib/tasks/sample_spec.rb

require 'rails_helper'
require 'rake'

describe 'sample' do
  before(:all) do
    @rake = Rake::Application.new
    Rake.application = @rake
    Rake.application.rake_require('sample', ["#{Rails.root}/lib/tasks"])
    Rake::Task.define_task(:environment)
  end


  describe 'sample' do
    subject { @rake['sample'].execute }

    it 'returns hoge' do
      user = create(:user)
      expect{ subject }.to change(User, :count).by(-1)
    end
  end
end