Stub class or instance methods on anything!

stub_method_chain.rb

class Object
  def metaclass
    class << self; self; end
  end

  def self.stub_method_chain chain, &blk
    chain = chain.split('.') if chain.is_a? String
    metaclass.instance_eval do
      define_method chain.first do |*values|
        Object.new.tap do |o|
          o.stub_method_chain chain.slice(1..-1), &blk
        end
      end
    end
  end
  
  def stub_method_chain chain, &blk
    chain = chain.split('.') if chain.is_a? String
    metaclass.instance_eval do
      define_method chain.first do |*values|
        if chain.size == 1
          blk.call *values
        else
          Object.new.tap do |o|
            o.stub_method_chain chain.slice(1..-1), &blk
          end
        end
      end
    end
  end
end

require 'minitest/autorun'

describe "stub method chain" do
  describe "class method" do
    before do
      @klass = Class.new
      @klass.stub_method_chain("foo.bar.baz") {|*args| "hi there!"}
    end
    
    it "stubs a chain of methods on a class" do
      @klass.foo.bar.baz.must_equal "hi there!"
    end
  end
  
  describe "instance method" do
    before do
      @obj = Object.new
      @obj.stub_method_chain("qux.qar.qi") {|*args| "hello!"}
    end
    
    it "stubs a chain of methods on an object" do
      @obj.qux.qar.qi.must_equal "hello!"
    end
  end
end

beast