minitest samples

custom_assertions.rb

# https://gist.github.com/2032303

module MiniTest::Assertions
  def assert_palindrome(string)                                                
    assert string == string.reverse, "Expected #{string} to read the same way backwards and forwards"
  end
    
  def assert_default(hash, default_value)
    assert default_value == hash.default, "Expected #{default_value} to be default value for hash but was #{hash.default.inspect}"
  end
end                                                                            

String.infect_an_assertion :assert_palindrome, :must_be_palindrome, :only_one_argument
Hash.infect_an_assertion   :assert_default, :must_default_to, :do_not_flip

shared_examples_for.rb

# https://gist.github.com/3113618

MiniTest::Spec.class_eval do                                                   
  def self.shared_examples                                                     
    @shared_examples ||= {}                                                    
  end                                                                          
end
                                                                               
module MiniTest::Spec::SharedExamples                                          
  def shared_examples_for(desc, &block)
    MiniTest::Spec.shared_examples[desc] = block                               
  end
                                                                               
  def it_behaves_like(desc)                                                    
    self.instance_eval do
      MiniTest::Spec.shared_examples[desc].call                                
    end
  end
end                                                                            
    
Object.class_eval { include(MiniTest::Spec::SharedExamples) }   

subject.rb

# https://gist.github.com/1116486

class MiniTest::Spec
  attr_accessor :subject

  def self.its msg, &block
    it msg.to_s do
      subject.send(msg).instance_eval &block
    end
  end
end

describe CashRegister do
  before do
    self.subject = CashRegister.new
  end

  describe "when empty" do
    its(:items) { must_be_empty }
    its(:total) { must_equal 0 }
  end

  describe "after scanning 1 and 2" do
    before do
      subject.scan(1)
      subject.scan(2)
    end
    its(:items) { wont_be_empty }
    its(:total) { must_equal 3 }
  end
end