eventually helper method for making assertions against asynchronous systems

async_helper.txt

# usage:
# it "should return a result of 5" do
#   eventually { long_running_thing.result.should eq(5) }
# end
module AsyncHelper
  
  def eventually(options = {})
    timeout = options[:timeout] || 2
    interval = options[:interval] || 0.1
    time_limit = Time.now + timeout
    
    loop do
      begin
        return if yield
      rescue RSpec::Expectations::ExpectationNotMetError, StandardError => error
      end

      raise error if Time.now >= time_limit
      sleep interval
    end
  end
end

# Can we put this into RSpec somewhere?

Hi, it looks like this might need 'return if error.nil?' on line 17 to support:

expect {}.to_not be_blank

which returns false, whereas:

expect ().to be_present

returns true

  loop do
    begin
      yield
    rescue RSpec::Expectations::ExpectationNotMetError, StandardError => error
    end

    return if error.nil?
    raise error if Time.now >= time_limit
    sleep interval
  end