Testing Puts

gistfile1.txt

class MyClass
  def initialize(word)
    @word = word
  end
  def putter
    puts @word
  end
end

describe "MyClass" do
  it "should put 'foo'" do
    myobj = MyClass.new('foo')
    myobj.should_receive(:puts).with('foo')
    myobj.putter
  end
end

puts is just a method that is mixed in to almost every object, so when you call puts, you are really calling self.puts which means you can use RSpecs mock expectations.

Notably, puts is not mixed into ruby 1.9's BasicObject, so if you try to do this:

class MyClass < BasicObject
  def putter
    puts 'foo'
  end
end

MyClass.new.putter

You'll get:

NoMethodError: undefined method `puts' for #<MyClass:0x00000100cdfae0>
        from (irb):3:in `putter'
        from (irb):6
        from /Users/Roberts/.rvm/rubies/ruby-1.9.3-p125-perf/bin/irb:16:in `<main>'

Which is kinda confusing, till you remember puts is just a method on your object, and BasicObject is a very bare object so has no puts.