Test Rake Tasks

Question

I am developing a ROR app that relies on many custom Rake tasks.

What is the best way to test them?

Answer 1

This is pretty well covered in another SO question

My recommendation, repeated here in summary, is not to try testing rake tasks: extract the code to be tested to a class, model or lib function and test it there. Then just use rake to call the functions and manage dependencies.

Answer 2

Well, now there's a Gem for that:

Fantaskspec - https://github.com/crismali/fantaskspec

Answer 3

I like the PivotalLabs' way the most. However, I generalized and modified their code as followed in my app:

# file: spec/tasks/my_rake_file_spec.rb
require 'spec_helper'
require 'rake'

describe 'my_rake_file.rake' do
  before :all do
    Rake.application.rake_require 'tasks/my_rake_file'
    Rake::Task.define_task(:environment)
  end

  let(:run_rake_task) {
    Rake::Task[task_name].reenable
    Rake.application.invoke_task task_name
  }

  describe 'my_task_name' do
    let(:task_name) { "my_task_name" }

    it "creates 10 cars" do
      run_rake_task
      Car.count.should == 10
    end
  end
end

Also, I extracted the heavy lifting of my_rake_file.rake's code to a module, which is stored in lib/

Answer 4

Rake tasks do need testing, especially if you do some batch processing in it. Testing them is quite easy these days:

class CleanExamsTaskTest < ActiveSupport::TestCase
  def test_deletes_results_of_old_exams
    travel_to Time.zone.parse('2010-07-05 10:00')
    @exam.update!(end: Time.zone.parse('2010-07-04 09:59'))

    assert_difference -> { @exam.answered_questions.count }, -1 do
      capture_io { run_task }
    end
  end

  def test_output
    travel_to Time.zone.parse('2010-07-05 10:00')
    @exam.update!(end: Time.zone.parse('2010-07-04 09:59'))

    assert_output("Exams processed: 1\n") { run_task }
  end

  private

  def run_task
    Rake::Task['exams:clean'].execute
  end
end

Full example

Tested with Ruby >= 1.9 and Rails 5.2. Uses Minitest from stdlib. No other dependencies.

Answer 5

Something like:

  def execute_rake(file,task)
    require 'rake'
    rake = Rake::Application.new
    Rake.application = rake
    Rake::Task.define_task(:environment)
    load "#{Rails.root}/lib/tasks/#{file}"
    rake[task].invoke
  end

At your spec:

execute_rake("tags.rake","tags:popular")

Answer 6

Rake tasks are pretty hard to test. The easiest solution would be to move the logic into a method in an appropriate model. You can then test that and just call the method from the rake task.