Rspec matchers for testing exit codes.

exit_code_matches.rb

require 'rspec/expectations'

module ExitCodeMatchers
  extend RSpec::Matchers::DSL

  matcher :terminate do
    actual = nil

    match do |block|
      begin
        block.call
      rescue SystemExit => e
        actual = e.status
      end
      actual and actual == status_code
    end

    chain :with_code do |status_code|
      @status_code = status_code
    end

    failure_message_for_should do |block|
      "expected block to call exit(#{status_code}) but exit" +
        (actual.nil? ? " not called" : "(#{actual}) was called")
    end

    failure_message_for_should_not do |block|
      "expected block not to call exit(#{status_code})"
    end

    description do
      "expect block to call exit(#{status_code})"
    end

    def status_code
      @status_code ||= 0
    end

  end

end

herp_derp_spec.rb

describe HerpDerps do

  # Fails with
  # NameError:
  #    undefined local variable or method `terminate' for 
  #    #<RSpec::Core::ExampleGroup::Nested_1::Nested_3::Nested_1:0x007ff96bac96f0>
  it 'exits cleanly' do
    # expecting call to `exit`
    -> { described_class.run }.should terminate
  end

  it 'exits with non-zero status code' do
    #expecting call to `abort` or `exit(false)`
    -> { described_class.run }.should terminate.with_code(1)
  end

end

Thanks, very useful.

Thanks for the convenient matcher. I've modified it for rspec 3.
https://gist.github.com/mmasashi/58bd7e2668836a387856