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MetricFu Gem Version Test Join the chat at Code Climate Inline docs

MetricFu is a set of tools to provide reports that show which parts of your code might need extra work.

Metrics supported: Cane, Churn, Flog, Flay, Reek, Roodi, Saikuro, Code Statistics, Hotspots, SimpleCov, Rcov, Rails Best Practices (Rails-only).



$ gem install metric_fu

Or add this line to your application's Gemfile:

gem 'metric_fu'

And then execute:

$ bundle


MetricFu is cryptographically signed. To be sure the gem you install hasn't been tampered with:

  • Add my public key (if you haven't already) as a trusted certificate gem cert --add <(curl -Ls
  • gem install metric_fu -P MediumSecurity

The MediumSecurity trust profile will verify signed gems, but allow the installation of unsigned dependencies.

This is necessary because not all of MetricFu's dependencies are signed, so we cannot use HighSecurity.


From your application root, run:

$ metric_fu

To see available options run metric_fu --help


MetricFu will attempt to load configuration data from a .metrics file, if present in your repository root.

MetricFu.report_name # by default, your directory base name
MetricFu.report_name = 'Something Convenient'

Example Configuration

# To configure individual metrics... do |config|
  config.configure_metric(:cane) do |cane|
    cane.enabled = true
    cane.abc_max = 15
    cane.line_length = 80
    cane.no_doc = 'y'
    cane.no_readme = 'y'

# Or, alternative format
MetricFu.configuration.configure_metric(:churn) do |churn|
  churn.enabled = true
  churn.ignore_files = ','
  churn.start_date = '6 months ago'

# Or, to (re)configure all metrics
MetricFu.configuration.configure_metrics.each do |metric|
  if [:churn, :flay, :flog].include?(
    metric.enabled = true
    metric.enabled = false

Rails Best Practices do |config|
  config.configure_metric(:rails_best_practices) do |rbp|
    rbp.silent = true
    rbp.exclude = ["config/chef"]

Coverage Metrics do |config|
  config.configure_metric(:rcov) do |rcov|
    rcov.coverage_file = MetricFu.run_path.join("coverage/rcov/rcov.txt")

If you want metric_fu to actually run rcov itself (1.8 only), don't specify an external file to read from

Rcov metrics with Ruby 1.8

To generate the same metrics metric_fu has been generating run from the root of your project before running metric_fu

RAILS_ENV=test rcov $(ruby -e "puts Dir['{spec,test}/**/*_{spec,test}.rb'].join(' ')") --sort coverage --no-html --text-coverage --no-color --profile --exclude-only '.*' --include-file "\Aapp,\Alib" -Ispec > coverage/rcov/rcov.txt

Simplecov metrics with Ruby 1.9 and 2.0

Add to your Gemfile or otherwise install

gem 'simplecov'

Modify your spec_helper as per the SimpleCov docs and run your tests before running metric_fu

#in your spec_helper
require 'simplecov'
require 'metric_fu/metrics/rcov/simplecov_formatter'
SimpleCov.formatter = SimpleCov::Formatter::MetricFu
# or
SimpleCov.formatter = SimpleCov::Formatter::MultiFormatter[

Additionally, the coverage_file path must be specified as above and must exist.


Built-in Formatters

By default, metric_fu will use the built-in html formatter to generate HTML reports for each metric with pretty graphs.

These reports are generated in metric_fu's output directory (tmp/metric_fu/output) by default. You can customize the output directory by specifying an out directory at the command line using a relative path:

metric_fu --out custom_directory    # outputs to tmp/metric_fu/custom_directory

or a full path:

metric_fu --out $HOME/tmp/metrics      # outputs to $HOME/tmp/metrics

You can specify a different formatter at the command line by referencing a built-in formatter or providing the fully-qualified name of a custom formatter.

metric_fu --format yaml --out custom_report.yml

Or in Ruby, such as in your .metrics

# Specify multiple formatters
# The second argument, the output file, is optional do |config|
  config.configure_formatter(:yaml, "customreport.yml")

Custom Formatters

You can customize metric_fu's output format with a custom formatter.

To create a custom formatter, you simply need to create a class that takes an options hash and responds to one or more notifications:

class MyCustomFormatter
  def initialize(opts={}); end    # metric_fu will pass in an output param if provided.

  # Should include one or more of...
  def start; end           # Sent before metric_fu starts metric measurements.
  def start_metric(metric); end   # Sent before individual metric is measured.
  def finish_metric(metric); end   # Sent after individual metric measurement is complete.
  def finish; end           # Sent after metric_fu has completed all measurements.
  def display_results; end     # Used to open results in browser, etc.


metric_fu --format MyCustomFormatter

See lib/metric_fu/formatter for examples.

MetricFu will attempt to require a custom formatter by fully qualified name based on ruby search path. So if you include a custom formatter as a gem in your Gemfile, you should be able to use it out of the box. But you may find in certain cases that you need to add a require to your .metrics configuration file.

For instance, to require a formatter in your app's lib directory require './lib/my_custom_formatter.rb'

Configure Graph Engine

By default, MetricFu uses the Bluff (JavaScript) graph engine.


But you can also use the Highcharts JS library


Notice: There was previously a :gchart option. It was not properly deprecated in the 4.x series.

Common problems / debugging


  • It is currently testing on MRI (>= 1.9.3), JRuby (19 mode), and Rubinius (19 mode). Ruby 1.8 is no longer supported.

  • For 1.8.7 support, see version 3.0.0 for partial support, or (where Semantic Versioning goes to die)

  • MetricFu no longer runs any of the analyzed code. For code coverage, you may use a formatter as documented above

  • The Cane, Flog, and Rails Best Practices metrics are disabled when Ripper is not available


Take a look at our contributing guide. Bug reports and pull requests are welcome on GitHub at This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Code of Conduct.



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