RSpec rake

invoke_rake_task.rb

# Could be placed in spec_helper.rb
# Requiring foo.rake in this example.

def run_foo_bar(arg)
  require 'rake'
  @rake = Rake::Application.new
  Rake.application = @rake
  Rake.application.rake_require "lib/tasks/foo"
  Rake::Task.define_task(:environment)
  silence do
    @task = Rake::Task["foo:bar"].invoke(arg)
  end
end

def silence
  begin
    orig_stderr = $stderr.clone
    orig_stdout = $stdout.clone

    $stderr.reopen File.new('/dev/null', 'w')
    $stdout.reopen File.new('/dev/null', 'w')

    return_value = yield
  rescue Exception => e
    $stdout.reopen orig_stdout
    $stderr.reopen orig_stderr
    raise e
  ensure
    $stdout.reopen orig_stdout
    $stderr.reopen orig_stderr
  end

  return_value
end