Using Rspec from irb

This is a quick guide showing you necessary steps you should take to make rspec to work on irb

Lets start by loading rspec core and expectations

require 'rspec/core'         #this is what really runs your tests
require 'rspec/expectations' #readable syntax for checking properties of your code 

We then include the matchers modules

include RSpec::Matchers 

rspec will NOT automatically include this for you if you are using irb

With this we can now test out our expectations:

>> expect(1).to eq(1)
=> true

Whooohoo! You are good to go.. Not really, try this out

2.3.0 :003 > array_hashes = [{lol: nil}]
 => [{:lol=>nil}] 
2.3.0 :005 > include RSpec::Matchers
 => Object 
2.3.0 :006 > expect(array_hashes).to include(have_key(:lol))

Rspec error while using rspec include on irb

You will encounter an error as shown below:

TypeError: wrong argument type RSpec::Matchers::BuiltIn::Has (expected Module)
 from (irb):6:in `include’
 from (irb):6
 from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>’

If you read closely into the error it expects a Module as an argument, this is because when using irb we are running in the main ruby object. This main ruby object has another method called include that has presidence over rspec’s include method

To work around this we can prepend RSpec::Matcher onto main’s singleton class:

$ irb
irb(main):001:0> require ‘rspec/expectations’
=> true
irb(main):002:0> singleton_class.prepend RSpec::Matchers
=> #<Class:#<Object:0x007ff08a8d6620>>
irb(main):003:0> array_hashes = [{lol: nil}]
=> [{:lol=>nil}]
irb(main):004:0> expect(array_hashes).to include(have_key(:lol))
=> true

We encountered this problem while doing a mob session at Agile Ventures and https://github.com/rspec/rspec-expectations/issues/1018 on the rspec expectations github page where we got this hack