RSpec 2 syntax cheat sheet by example

rspec-syntax-cheat-sheet.rb

# RSpec 2.0 syntax Cheet Sheet by http://ApproachE.com

# defining spec within a module will automatically pick Player::MovieList as a 'subject' (see below)
module Player
  describe MovieList, "with optional description" do

    it "is pending example, so that you can write ones quickly"

    it "is already working example that we want to suspend from failing temporarily" do
      pending("working on another feature that temporarily breaks this one")
      # actual test code is here, will never be reached
    end

    it "is pending when failing" do
      pending "This will be marked as pending when the block will fail, otherwise (on success) will fail telling 'Why am I pending if I pass?'" do
        1.should == 2 # will mark example as pending
        2.should == 2 # will fail asking to remove pending status of example
      end
    end

    # this will automatically generate name of the example based on the expectations inside it ~ 'it' with no description
    specify { [1,2,3].should have(3).items }

    #any helper methods, before/after, modules etc declared in the outer group are available in the inner group.
    describe "outer" do
      before(:each) { puts "first" }
      describe "inner" do
        before(:each) { puts "second" }
        it { puts "third"}
        after(:each) { puts "fourth" }
      end
      after(:each) { puts "fifth" }
    end

    # 'describe' and 'context' are equivalent
    # I prefer to use 'context' for defining an 'environment'
    context "when first created" do
      it "is empty" do
        movie_list = MovieList.new
        movie_list.should be_empty
      end
    end

    # I prefer to use 'describe' for nouns, verbs; defining a nested set of specifications
    describe "forward" do
      it "should jump to a next movie" do
        next_movie = MovieList.new(2).forward
        next_movie.track_number.should == 2
      end
    end
  end

  it "will have default subject that corresponds to the instance of first parameter in 'describe'" do
    subject.class.should be == MovieList
  end
  # unless subject is set explicitly
  subject { MovieList.new(10) } # approximately similar to 'before(:each)'
  # no need to use 'subject.should', use 'should'
  specify { should have(10).items } # same as below
  specify { subject.should have(10).items }


  # similar to specify { subject.track_number.should == 1}
  its(:track_number) { should == 1 }

  context "specs set-up" do
    # we can run setup before each examle, or all of them
    before(:each) do    
      @new_on_each_example = YourObject.new
    end
    before do
      @new_on_each_spec_less_verbose = YourObject.new
    end
    before(:all) do
      # Avoid using it as it will bring the 'shared state' into unit tests
      @same_instance_for_all_examples_within_the_context = YourObject.new
    end    
    it "can access attributes defined in 'before'" do
      @new_on_each_example.should_not be_nil
      @same_instance_for_all_examples_within_the_context.should_not be_nil
    end

    # cleanup code can be run the same way using 'after' instead of 'before'
    # Avoid using 'after'    
    # we can wrap examples: before + after + manual handling
    # In most cases 'before' + 'after' will work better.
    around do |example|      
      DB.transaction { example.run }
      # should handle errors manually, so do not do something like:
      # DB.start_transaction
      # example.run
      # DB.rollback_transaction
    end
    it "should run within a transaction" do
      MovieList.new.save!
    end    

    let(:new_on_each_example) { ObjectPerExample.new }
    it "can use method defined by 'let'" do
      new_on_each_example.should_not be_nil
      # the object is memoized, so
      new_on_each_example.should == new_on_each_example
    end

    # defining helper methods within context may be more useful than setup
    def forward(times) do
      list = MoviewList.new(10)
      list.forward(times).track_number
    end
    it "can use it multiple times" do
      forward(1).should == 1
      forward(2).should == 2
      forward(10).should == 1
    end

    # using 'yield' with helper methods
    def given_thing_with(options)
      yield Thing.new do |thing|
        thing.set_status(options[:status])
      end
    end
    it "should do something when ok" do
      given_thing_with(:status => 'ok') do |thing|
        thing.do_fancy_stuff(1, true, :move => 'left', :obstacles => nil)
      end
    end


    # helpers can come from modules
    module Helpers
      def shared_help
        [1,2,3]
      end
    end
    include Helpers
    it "can use helpers from Module" do
      shared_help.should == [1,2,3]
    end
    # or this module can be included for ALL example groups automatically during configuration:
    # RSpec.configure do |config|
    #  config.include Helpers
    # end
  end


  context "built-it stubbing, faking, mocking" do
    it "can stub" do
      source = double('source')      
      source.stub(:fetch) { [1,2,3,4,5] }      
      source.stub(:fetch_from).and_return([1,2]) # other way      
      MovieList.stub(:find).and_return(MovieList.new) # stub class method

      implementing = double('source')
      implementing.stub(:fetch) do |count|
        count == 5 ? [1,2,3] : [4,5,6,7] # provide stub logic here, easy to use for Fakes
      end      
      # easily stub chains of calls
      Blog.stub_chain(:posts, :published, :recent).and_return([1,2,3])
      Blog.posts.published.recent.should == [1,2,3]
    end
    it "can ignore non-expected method calls (NullObject pattern)" do
      source = double('source', :url => 'http://example.com').as_null_object      
      source.any_method_call_onwill_return_nil.should be_nil
      # the source mock object will record the 'any_method_call_onwill_return_nil' message internally though      
    end
    it "can set expectations" do
      source = double('source')
      # arguments
      source.should_receive(:fetch).with(10, "abc").and_return([1,2]) # expecting arguments (10, "abc") otherwise failing
      source.should_receive(:fetch).with(instance_of(Integer), "abc").and_return([1,2]) # don't care about 1st argument as long as it is Integer
      source.should_receive(:fetch).with(10, anything).and_return([1,2]) # don't care about 2nd argument at all
      source.should_receive(:fetch).with(any_args) # same as not using 'with' - don't care about arguments
      source.should_receive(:fetch).with(no_args) # 0 arguments, otherwise fail
      source.should_receive(:fetch).with(hash_including(:count => 10, :url => 'abc')) # arg should be Hash with all the values mentioned
      source.should_receive(:fetch).with(hash_not_including(:timeout => 5)) # arg should be Hash that contains no ':timout=>5'
      source.should_receive(:fetch).with(anything, /example/) # 2nd arg shuold match RegEx
      source.should_receive(:fetch).and_return([1], [1,2], [1,2,3]) # 1st call - [1], 2nd - [1,2], 3rd - [1,2,3], 4th - [1] and so on ...
      # expectation overrides stub
      source.stub(:fetch).and_return([1,2]) # will return [1,2] when called
      source.should_recieve(:fetch).and_return([3,4]) # prev been overriden and will return [3,4]
      # raising/throwing
      source.should_receive(:fetch).and_raise # raise Exception
      source.should_receive(:fetch).and_raise(ZeroDivisionError) # raise ZeroDivisionError
      source.should_receive(:fetch).and_raise(Exception.new('instance of aexception')) # raise given exception
      source.should_receive(:fetch).and_throw(:zero) # thro :zero          
      # order
      source.should_receive(:first).ordered # order matters in relation to others marked as ordered
      source.should_receive(:dosnt_matter) # don't care about order as long as it is called
      source.should_receive(:second).ordered # must be called after 'first'
      # order is not enforced across different objects:
      double('a').should_receive(:a).ordered # not related to the next one
      double('b').should_receive(:b).ordered # not related to the prev one
      # how many times?
      source.should_recieve(:fetch).exactly(1)times
      source.should_recieve(:fetch).at_most(5)times
      source.should_recieve(:fetch).at_least(2)times
      source.should_recieve(:fetch).twice
      source.should_recieve(:fetch).once
      # negative expectations
      source.should_recieve(:fetch).never
      source.should_recieve(:fetch).exactly(0)times
      source.should_not_recieve(:fetch)      


      list = MovieList.new(source)
      # if source.fetch has not been called, then example will fail
    end

    context "custom expectations" do
      # define custom expection class somewhere
      class GreaterThanMatcher
        def initialize(expected)
          @expected = expected
        end
        def description
          # will generate proper failure message and name of the example
          "a number greater than #{@expected}"
        end
        def ==(actual)
          # this will be called from
          actual > @expected
        end
      end

      # add this method to the RSpec (see set-up for global configuration)
      def greater_than(floor)
        GreaterThanMatcher.new(floor)
      end

      it "can be used in expectations" do
        subject.should_recieve(:forward).with(greater_than 3)
        subject.forward(5)
      end
    end # custom matchers
  end # mocking





  # set of same examples shared accross multiple specs
  # shared_examples_for should be in a separate file and defined outside of 'describe'/'context'
  shared_examples_for "any pizza" do
    it "tastes really good" do
      @pizza.should taste_really_good
    end
  end

  # to include the shared examples, into example groups:
  # it will assume @pizza instance variable is available here
  it_behaves_like "any pizza"

  context 'defining examples dynamically - everybody knows that :)' do
    {2 => 4, 3 => 6, 10 => 20}.each do |input, output|
      it "#{input} * 2 should be equal to #{output}" do
        (input * 2).should == output
        # will produce examples:
        # - 2 * 2 should be equal to 4
        # - 3 * 2 should be equal to 6
        # - 10 * 2 should be equal to 20
      end
    end
  end


  context "matchers" do
    it "shows built-in matchers" do
      # TODO: describe ===, eql, equal
      1.should == 1
      1.should_not == 2 # NOT 1.should != 2
      1.should_not equal(2) # same as above
      1.should_not == 2
      5.should be > 3
      5.should be <= 5
      (1.251).should be_close(1.25, 0.005)
      (1.251).should be_within(0.005).of 1.25 # >= RSpec 2.1
      "reg exp".should =~ /exp/
      [1,2].should include(1)
      1.should respond_to(:to_s)

      true.should be_true
      0.should be_true
      "this".should be_true

      lambda { Object.new.explodde! }.should raise_error(NameError)

      # nothing fits
      5.should satisfy { |it| it == 5 }
    end

    it "shows cool things" do
      count = 1
      expect {
        count = 3
      }.to change { count }.by(2)

      expect {
        # not changing
      }.to_not change { count }

      count = 1
      expect {
        count = 3
      }.to change { count }.to(3)

      count = 1
      expect {
        count = 3
      }.to change { count }from(1).to(3)

      # raise-rescue - exception handling
      expect {2 / 0}.to raise_error("divided by 0")
      expect {2 / 0}.to raise_error(/by 0/)
      expect {2 / 0}.to raise_error(ZeroDivisionError)

      # try-catch - expected circumstance handling
      lambda {  throw :room_is_full }.should throw_symbol(:room_is_full)

      # predicates
      nil.should be_nil #call nil.nil?
      [].should be_empty # calls [].empty?
      [1,2,3].should_not be_empty # calls [1,2,3].empty

      # convert anything that begins with have_ to a predicate on the target object beginning with has_
      {:id => 1}.has_key?(:id).should == true
      # can be written as
      {:id => 1}.should have_key(:id) # calls {:id => 1}.has_key?(:id)

      # collections      
      obj = {}
      def obj.numbers
        [1,2,3,4]
      end

      obj.should have(4).numbers # calls obj.numbers.length
      [1,2,3,4].should have(4).items # 'items' is 'reserved' to say "ensure number of items on the collection"
      [1,2,3,4].should be_any {|n| n % 2 == 0} # [1,2,3,4].any? {|n| n %% 2 == 0}.should be_true
      "stringy".should have(7).charaters # same as items, just syntactic sugar
      [1,2,3,4].should have_exactly(24).items # same as 'have'
      obj.should have_at_least(3).numbers


    end
  end # built-in matchers





  context "custom matchers" do
    # TODO: describe multiple ways

    #define class
    class SimilarTo
      # mandatory - link to the object under test
      def initialize(it)
        # object under test
        @it = it
      end      
      # mandatory - check the positive condition
      def matches?(that)
        @that = that # save to use it in messages
        @that.to_s.downcase.should == @it.to_s.downcase
      end
      # optional - opoosite to mathch?
      def does_not_matche?(that)
        result = !matches?(that)
        @that, @it = @it, @that # swap for negative condition or additionally cusomtize messages
        result # don't forget to return
      end
      # mandatory
      def failure_message_for_should
        "expected #{@it} to be similar to #{@that}"
      end
      # optional
      def failure_message_for_should_not
        "expected #{@it} to be different from #{@that}"
      end
      #optional
      def description
        "#{@it} should be similar to #{@that}"
      end
    end

    #define method on example (see set-up to incude in all examples)
    def similar_to(that)
      SimilarTo.new(that)
    end
  end # custom matchers




  context "macros" do
    module ControllerMacros    
      def should_render(template)
        it "should render the #{template} template" do
          do_request
          response.should render_template(template)
        end
      end

      def should_assign(hash)
        variable_name = hash.keys.first
        model, method = hash[variable_name]
        model_access_method = [model, method].join('.')
        it "should assign @#{variable_name} => #{model_access_method}" do
          expected = "the value returned by #{model_access_method}"
          model.should_receive(method).and_return(expected)
          do_request
          assigns[variable_name].should == expected
        end
      end

      def get(action)
        define_method :do_request do
          get action
        end
        yield
      end
    end

    RSpec.configure do |config|
      config.use_transactional_fixtures = true
      config.use_instantiated_fixtures  = false
      config.fixture_path = RAILS_ROOT + '/spec/fixtures/'
      config.extend(ControllerMacros, :type => :controller)
    end    
  end # macros

end # module