A fist full of code metrics
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Version 0.7.1

Metric_fu began its life as a plugin for Rails that generated code metrics reports.  As of version 0.7.0, metric_fu is a gem owing to the excellent work done by Sean Soper.  

Metric_fu is a set of rake tasks that make it easy to generate metrics reports.  It uses Saikuro, Flog, Rcov, and Rails' built-in stats task to create a series of reports.  It's designed to integrate easily with CruiseControl.rb by placing files in the Custom Build Artifacts folder.

sudo gem install jscruggs-metric_fu -s http://gems.github.com

Then in your Rakefile:
require 'metric_fu'

*Important note:
You must have Rcov and Flog installed to get coverage and flog reports.  You can do this through ruby gems at the command line like so:
sudo gem install rcov
sudo gem install flog


Out of the box metrics provides these tasks:
rake metrics:all              
rake metrics:all_with_migrate
rake metrics:coverage
rake metrics:saikuro
rake metrics:flog
rake metrics:stats
rake metrics:churn

See below for more detail on the individual tasks.  It's recommended to use CruiseControl.rb to set up a metrics build.  See the CruiseControl.rb online docs for more info on how to set up cc.rb and, once you've got that figured out, change the cruise_config.rb file inside your project to have these lines:

project.rake_task = 'metrics:all_with_migrate'
project.scheduler.polling_interval = 24.hours

Which will check for updates every 24 hours and run all the metrics rake tasks (migrating your test db first).  The output will be visible from an individual build's detail page.

*Notes on metrics:coverage

When creating a coverage report, metric_fu runs all the tests in the test folder using Rcov.  If you use RSpec you can change the default by putting this in your Rakefile:

namespace :metrics do
  TEST_PATHS_FOR_RCOV = ['spec/**/*_spec.rb']

The namespace is only there for intentional purposes and isn't necessary.  If you have multiple paths to test, then you can do this:

  TEST_PATHS_FOR_RCOV = ['spec/**/*_spec.rb', 'test/**/*_test.rb']

The coverage task will iterate over all the paths and aggregate the results into one report. You'll see a coverage.data file in the root of your project.

If you want to change the options that Rcov is run with, then set this constant in your Rakefile:

  RCOV_OPTIONS =  { "--sort" => "loc" }

It's a hash that gets merged with the default options.  This particular change will sort the coverage report by lines of code (loc).  Check out the Rcov documentation for more options.  If you want to see the default options metric_fu runs, open up the rake files in the plugin.

*Notes on metrics:cyclomatic_complexity

Saikuro is bundled with metric_fu so you don't have to install it.  Look at the SAIKURO_README (or the internet) for more documentation on Saikuro.  If you wish to change the options Saikuro is run with, then set this constant in your Rakefile:

namespace :metrics do                   
  SAIKURO_OPTIONS = { "--warn_cyclo" => "3", "--error_cyclo" => "4" }

Like RCOV_OPTIONS, SAIKURO_OPTIONS is a hash that gets merged with the default options hash.  The above example will set the warn_cyclo to 3 and the error_cyclo to 4 (which is way too low -- it's just an example) instructing Saikuro to flag methods with a higher cyclomatic complexity in it's report.

*Notes on metrics:flog

Flog is another way of measuring complexity (or tortured code as the Flog authors like to put it).  Metric_fu takes the output of Flog run on the 'app' folder, puts it in between some <pre> tags, calculates the average Flog score per method, and jams all that into an index.html file.  You should check out the awesome, and a little scary, Flog website for more info.

*Notes on metrics:stats

This is just 'rake stats' put into a file.  On my projects I like to be able to look at CruiseControl and get stats about the app at different points in time.

*Notes on metrics:churn

Files that change a lot in your project may be bad a sign.  This task uses "svn log" to identify those files and put them in a report.  The default is to start counting changes from the beginning of your project, which might be too far back so you can change like so:

namespace :metrics do 
  CHURN_OPTIONS = { :start_date => lambda{3.months.ago} }

The Proc is there because '3.months.ago' only works when after the Rails Environment is loaded (and Rails extends Fixnum) which I didn't want to do every time you run a rake task.

You can also change the minimum churn count like so:

namespace :metrics do
  CHURN_OPTIONS = { :minimum_churn_count => 3 }


I'd like to thank the authors of Saikuro, Flog, Rcov, CruiseControl.rb, and Rails for creating such excellent open source products.  Also Michael Schubert, Kurtis Seebaldt, Toby Tripp, Paul Gross, and Chirdeep Shetty for their help and advice.