Friday, 7 August 2009

Faking startup and shutdown with ActiveSupport::TestCase

Time-was we didn't just have setup and teardown in our Tests (which are run for every single test case)... we could also have a startup/shutdown pair that ran once per proper Test-case class (ie once at the beginning of all tests in a set).

This was a perfect place to put run-once-only things - especially useful if, say, you wanted to run ruby-prof over your tests. You could put the RubyProf.start in startup and have it print out a callgraph in the shutdown...

ActiveSupport::TestCase doesn't let us have our startup/shutdown anymore... so what to do?

Fake it with at_exit

  # quick-and-dirty class var to tell us if we've already registered the
  # at_exit RubyProf function.
  @@register_done = false
  # register the stop-ruby-prof stuff
  # We want it to spit out a RubyProf callgraph after it's run this test
  # case.
  # You can either: call this function directly in a single test case or
  # test-suite eg: "register_rubyprof"
  # If you pass a value to "RUN_RUBY_PROF" on the command-line - it will
  # also run this register function for you. eg:
  # RUN_RUBY_PROF=true rake test:units TEST=test/unit/widget_test.rb
  def register_rubyprof
    require 'ruby-prof'
    return if @@register_done
    p "starting RubyProf"

    path_base = "#{RAILS_ROOT}/tmp/performance/ruby-prof"

    p "started! Now registering exit-function"
    at_exit do
      p "All done - stopping RubyProf" 
      result = RubyProf.stop

      p "Stopped! now printing call graph"
      timestamp ='%Y-%m-%d-%H-%M-%S')
      # try and make the callgraph filename meaningful to the test-run
      filename_base = "rubyprof_#{}_#{timestamp}"

      # Print a call tree profile to text for kcachegrind to use
      printer =
      printer.print("#{path_base}/#{filename_base}_calltree.txt", 'w'), 0)
      p "All Done. Good luck profiling!"
    @@register_done = true
  # will setup the reguster-rubyprof function if we have set the
  # RUN_RUBYPROF constant to true
  setup :register_rubyprof if RUN_RUBY_PROF


Daniel Berger said...

There's startup and shutdown in test-unit 2.x. If you require the test-unit gem first, won't its features automatically be available in ActiveSupport::TestCase?

Taryn said...

For some reason I thought that ActiveSupport::TestCase inherited from Test::Unit somehow...

I guess I could re-include it if it's necessary - but it seems a bit like overkill just to add a startup/shutdown.