match_stream.rb

require 'rspec/expectations'

RSpec::Matchers.define :match_stream do |expected_stream|
  match do |actual_stream|
    loop do
      actual_element = actual_stream.next rescue :eof
      expected_element = expected_stream.next rescue :eof
      return false unless actual_element == expected_element
      return true if actual_element == :eof
    end
  end
end

test.tb

expected_enum = some_array_or_file.each.lazy # or some other of enum

it 'returns an enum with the values' do
  expect(subject.call).to match_stream(expected_enum)
end