Mocha VS MiniTest::Mock and SimpleDelegate VS SimpleMock

benchmark.rb

 require 'benchmark'
 require 'delegate'
 require 'mocha'
 require 'simple_mock'
 require 'rr'
 
 extend RR::Adapters::RRMethods
 
 n = 1000
 array = [1]
 Benchmark.bm(10) do |x|
   x.report 'mocha' do
     n.times do
       array.expects(:push).with(2).returns([1, 2])
       array.push(2)
     end
   end
   x.report 'delegator' do
     n.times do
       mock  = Class.new(SimpleDelegator) { def push(*args); [1, 2]; end }.new(array)
       mock.push(2)
     end
   end
   x.report 'simple_mock' do
     n.times do
       mock  = SimpleMock.new(array).expect(:push, [1, 2], [2])
       mock.push(2)
     end
   end
   x.report 'rr' do
     n.times do
       mock = mock(array).push(2).returns([1, 2])
       mock.push(2)
     end
   end
 end

benchmark.txt

                 user     system      total        real
mocha        1.660000   0.010000   1.670000 (  1.721667)
delegator    0.010000   0.000000   0.010000 (  0.011092)
simple_mock  0.020000   0.000000   0.020000 (  0.016473)
rr

Error.txt

⮁ ruby benchmark.rb > benchmark.txt 
benchmark.rb:33:in `block (3 levels) in <main>': undefined method `push' for #<RR::DoubleDefinitions::DoubleDefinition:0x007fe9aa28e240> (NoMethodError)
        from benchmark.rb:31:in `times'
        from benchmark.rb:31:in `block (2 levels) in <main>'
        from /Users/costro0001/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/benchmark.rb:280:in `measure'
        from /Users/costro0001/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/benchmark.rb:362:in `item'
        from benchmark.rb:30:in `block in <main>'
        from /Users/costro0001/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/benchmark.rb:174:in `benchmark'
        from /Users/costro0001/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/benchmark.rb:205:in `bm'
        from benchmark.rb:11:in `<main>'

I tried to add in a comparison of RR, but I couldn't figure out what I was doing incorrectly.