nutrun

Synthesis visualizations

Synthesized testing is about accurately simulating object interactions and verifying that each end point of every interaction has been tested to work. The end result of a code base tested employing this strategy forms a specification of the application's ecosystem in terms of object communication.

Danilo has been recently contributing some excellent work around visual representations of the above. The code is being developed on the Synthesis experimental branch on github.

Consider the Synthesis test_project example.

class DataBrander
  BRAND = "METAL"

  def initialize(storage)
    @storage = storage
  end

  def save_branded(data)
    @storage.save "#{BRAND} - #{data}"
  end

  def dont_do_this
    @storage.ouch!
  end
end

class Storage
  def initialize(filename)
    @filename = filename
  end

  def save(val)
    File.open(@filename, 'w') {|f| f < val}
  end

  def ouch!
    raise Problem
  end
end

class Problem < Exception;end

Below are the complete specs for the above implementation.

describe DataBrander do
  it "should save branded to storage" do
    storage = Storage.new("")
    storage.should_receive(:save).with("METAL - rock")
    DataBrander.new(storage).save_branded("rock")
  end

  it "should delegate problem" do
    storage = Storage.new("")
    storage.should_receive(:ouch!).and_raise(Problem.new)
    proc {DataBrander.new(storage).dont_do_this}.should raise_error(Problem)
  end
end

describe Storage do
  it "should save to file" do
    begin
      Storage.new("test.txt").save("rock")
      File.read("test.txt").should == "rock"
    ensure
      FileUtils.rm_f("test.txt")
    end
  end
  
  it "should raise problem on ouch!" do
    proc { Storage.new("").ouch! }.should raise_error(Problem)
  end
end

A Synthesis run using the DOT formatter produces:

Removing the "should save to file" spec will cause the Synthesis task to fail.

Below is how a real (relatively small) project looks like.

I find the ability to inspect our application modeling through such a representation a very appealing added benefit to the confidence in our system Synthesis provides us with. The DOT formatter will become part of the Synthesis gem as soon as we iron out the few remaining glitches.