Thread Queue Kata: A Property Based TDD Kata in Ruby using Rantly

Introduction

Setup

You have ruby installed.

You have git installed.

git clone https://github.com/zhon/thread-queue-kata

You have bundle installed (gem install bundle)

bundle install

0. Coming up to speed

1. Story: Write a Threaded Queue

1.0.0 Fail (Red)

test/thread_queue_test.rb

describe ThreadQueue do

  it 'runs all jobs' do
    property_of {
      range 1, 100
    }.check {|tc|
      count = 0
      tp = ThreadQueue.new(tc)
      tc.times do
        tp.add -> { count += 1  }
      end
      count.must_equal tc
    }
  end

end

1.0.1. Pass (Green)

lib/thread_queue.rb

class ThreadQueue

  def initialize *args
  end

  def add item
    item.call
  end

end

1.0.2 Fail

test/thread_queue_test.rb

  it 'runs jobs concurrently' do
    property_of {
      range 1, 10
    }.check {|tc|
      tp = ThreadQueue.new(tc)
      t = Time.now.to_f
      tc.times do
        tp.add -> { sleep 0.01  }
      end
      (Time.now.to_f - t).must_be :<, 0.01 + 0.002 * tc , "Thread count #{tc}"
    }
  end

1.0.3 Pass (sorta)

lib/thread_queue.rb

  def add item
    Thread.new {
      item.call
    }
  end

test/thread_queue_test.rb

  it 'runs all jobs' do
    .
    .
    .
      tc.times do
        tp.add -> { count += 1  }
      end
+      sleep 0.003
      count.must_equal tc
    }
  end

1.0.4 Refactor

test/thread_queue_test.rb

  it 'runs all jobs' do
      tc.times do
        tp.add -> { count += 1  }
      end
-      sleep 0.003
+      tp.join
      count.must_equal tc
    }
  end

lib/thread_queue.rb

class ThreadQueue
  .
  .
  .
  def join
    sleep 0.003
  end

1.0.5 Refactor to real implementation

Sleep in an implementation is a code smell.

lib/thread_queue.rb

class ThreadQueue

  def initialize *args
    @threads = []
  end

  def add item
    @threads << Thread.new {
      item.call
    }
  end

  def join
    @threads.each(&:join)
  end

end

Join will help out our concurrent test also.

test/thread_queue_test.rb

  it 'runs jobs concurrently' do
    .
    .
    .
      tc.times do
        tp.add -> { sleep 0.01  }
      end
+      tp.join
      (Time.now.to_f - t).must_be :<, 0.01 + 0.002 * tc , "Thread count #{tc}"
    }
  end