Running a Rake task with parameters

Question

I have been working to get test coverage on the following rake task with the attached spec. However, nothing I appear to try sends the env parameter through correctly?

Test Failures

  1) myapp:database tasks myapp:database :recreate works
     Failure/Error: system("RAILS_ENV=#{args[:env]} rake db:create")

       main received :system with unexpected arguments
         expected: (/RAILS_ENV=testing rake db:drop/)
              got: ("RAILS_ENV=testing rake db:create")
       Diff:
       @@ -1,2 +1,2 @@
       -[/RAILS_ENV=testing rake db:drop/]
       +["RAILS_ENV=testing rake db:create"]

     # ./lib/tasks/database.rake:9:in `block (3 levels) in <top (required)>'
     # ./spec/lib/tasks/database_rake_spec.rb:17:in `block (5 levels) in <top (required)>'
     # ./spec/lib/tasks/database_rake_spec.rb:17:in `block (4 levels) in <top (required)>'
     # -e:1:in `<main>'

Spec

describe 'myapp:database tasks' do
  include_context 'rake'
  let(:task_paths) { ['tasks/database', 'tasks/seed'] }

  # rubocop:disable RSpec/MultipleExpectations
  describe 'myapp:database' do
    before do
      invoke_task.reenable
    end

    # TODO!
    context ':recreate', focus: true do
      let(:task_name) { 'myapp:database:recreate' }

      it 'works' do
        expect_any_instance_of(Object).to receive(:system).with(/RAILS_ENV=testing rake db:drop/).and_return(true)
        expect { invoke_task.invoke('testing') }.to output(
          "\nDropping the testing database\n"\
          "\nCreating the testing database\n"\
          "\nRunning the testing database migrations\n"
        ).to_stdout
      end
    end

    # rubocop:disable RSpec/MessageSpies
    context ':reset' do
      let(:task_name) { 'myapp:database:reset' }

      it 'works' do
        expect(Rake::Task['myapp:database:recreate']).to receive(:invoke).twice
        expect(Rake::Task['myapp:seed:all']).to receive(:invoke)
        expect { invoke_task.invoke }.to output("\nResetting the development and testing databases\n").to_stdout
      end
    end
  end
  # rubocop:enable all
end

Task

namespace :myapp do
  namespace :database do
    if Rails.env.development? || Rails.env.test?
      desc 'Drop and create a database, ["env"] = environment'
      task :recreate, [:env] => [:environment]  do |_t, args|
        puts "\nDropping the #{args[:env]} database\n"
        system("RAILS_ENV=#{args[:env]} rake db:drop")
        puts "\nCreating the #{args[:env]} database\n"
        system("RAILS_ENV=#{args[:env]} rake db:create")
        puts "\nRunning the #{args[:env]} database migrations\n"
        system("RAILS_ENV=#{args[:env]} rake db:migrate")
      end

      desc 'Reset the db data and setup development'
      task reset: :environment do
        puts "\nResetting the development and testing databases\n"
        %w(development test).each do |db|
          Rake::Task['myapp:database:recreate'].invoke(db)
        end
        Rake::Task['myapp:seed:all'].invoke
      end
    end
  end
end

Shared Context

shared_context 'rake' do
  let(:invoke_task) { Rake.application[task_name] }
  let(:highline) { instance_double(HighLine) }

  before do
    task_paths.each do |task_path|
      Rake.application.rake_require(task_path)
    end
    Rake::Task.define_task(:environment)
  end

  before do
    allow(HighLine).to receive(:new).and_return(highline)
    # rubocop:disable all
    allow_any_instance_of(Object).to receive(:msg).and_return(true)
    allow_any_instance_of(Object).to receive(:error_msg).and_return(true)
    # rubocop:enable all
  end
end

Update

context ':recreate' do
  let(:task_name) { 'myapp:database:recreate' }

  it 'works' do
    expect_any_instance_of(Object).to receive(:system).with(/RAILS_ENV=testing rake db:drop/).and_return(true)
    expect_any_instance_of(Object).to receive(:system).with(/RAILS_ENV=testing rake db:create/).and_return(true)
    expect_any_instance_of(Object).to receive(:system).with(/RAILS_ENV=testing rake db:migrate/).and_return(true)
    expect { invoke_task.invoke('testing') }.to output(
      "\nDropping the testing database\n"\
      "\nCreating the testing database\n"\
      "\nRunning the testing database migrations\n"
    ).to_stdout
  end
end

Answer 1

As I mentioned in a comment, the task isn't being invoked from the test because of the way you're stubbing here:

    expect(Rake::Task['myapp:seed:all']).to receive(:invoke)

Although this checks whether invoke was called, it doesn't actually invoke invoke (actually, it makes the method return nil). To change that, you can either:

1. tack on an and_return(<something>)
2. tack on and_call_original.

Probably in this case you'd want to use and_call_original since you want to investigate what actually happens in the task. In order to stub individual method calls in the task, the approach you have been using (expect_any_instance_of(Object).to receive(:system)) will technically work, but could probably be refactored to be more decoupled from the code.

For example, you could separate each system call into its own method (available to the rake task), and then call those from the test. Then in order to stub it you only need to pass the method name. If you want, you can then go and unit test each of those methods individually, putting the system call expectation in there.

I don't recall where exactly but I've heard it advised to not do any acual programming in Rake tasks. Put your code somewhere in your regular codebase, and call those methods from the rake task. This can be seen as an example of a more general pattern which is to refactor large methods into smaller ones. Writing code this way (and also with a functional style, but I won't get into that) makes your life easier when testing.

---

onto your followup question:

as you can see in the test case's failure message, the only difference between the actual and expected is that one is a regex and the other is a string.

A simple fix for this is to change this line:

    expect_any_instance_of(Object).to receive(:system).with(/RAILS_ENV=testing rake db:drop/).and_return(true)

so that the with() argument is a string, not a regex