become_matcher.rb

become_matcher.rb

require "timeout"

RSpec::Matchers.define :become do |expected|
  supports_block_expectations

  match do |block|
    begin
      Timeout.timeout(Capybara.default_wait_time * 3) do
        sleep(0.1) until (@actual = block.call) && @actual == expected
        true
      end
    rescue TimeoutError
      false
    end
  end

  failure_message do
    "expected #{@actual.inspect} to become #{expected.inspect}"
  end
end