Code coverage for Ruby 1.9
Important Notice: There is currently a bug that affects exit code handling on the 0.8 line of SimpleCov, see #281. Please use gem 'simplecov', '~> 0.7.1'
until this is resolved.
SimpleCov is a code coverage analysis tool for Ruby 1.9. It uses 1.9's built-in Coverage library to gather code coverage data, but makes processing its results much easier by providing a clean API to filter, group, merge, format and display those results, thus giving you a complete code coverage suite that can be set up with just a couple lines of code.
In most cases, you'll want overall coverage results for your projects, including all types of tests, cucumber features etc. SimpleCov automatically takes care of this by caching and then merging results when generating reports, so your report actually includes coverage across your test suites and thereby gives you a better picture of blank spots.
The official formatter of SimpleCov is packaged as a separate gem called simplecov-html but will be installed and configured automatically when you launch SimpleCov. If you're curious, you can find it on Github, too.
- Add SimpleCov to your
Gemfile
andbundle install
:
gem 'simplecov', :require => false, :group => :test
- Load and launch SimpleCov at the very top of your
test/test_helper.rb
(orspec_helper.rb
, cucumberenv.rb
, or whatever your preferred test framework uses):
require 'simplecov'
SimpleCov.start
# Previous content of test helper now starts here
Note: If SimpleCov starts after your application code is already loaded (via require
), it won't be able to
track your files and their coverage! The SimpleCov.start
must be issued before any of your application code
is required!
SimpleCov must be running in the process that you want the code coverage analysis to happen on. When testing a server
process (i.e. a JSON API endpoint) via a separate test process (i.e. when using Selenium) where you want to see all
code executed by the rails server
, and not just code executed in your actual test files, you'll want to add something
like this to the top of script/rails
:
if ENV['RAILS_ENV'] == 'test'
require 'simplecov'
SimpleCov.start 'rails'
puts "required simplecov"
end
-
Run your tests, open up
coverage/index.html
in your browser and check out what you've missed so far. -
Add the following to your
.gitignore
file to ensure that coverage results are not tracked by Git (optional):coverage
If you're making a Rails application, SimpleCov comes with a built-in configurations (see below for information on profiles) which will get you started with groups for your Controllers, Views, Models and Helpers. To use it, the first two lines of your test_helper should be like this:
require 'simplecov'
SimpleCov.start 'rails'
Coverage results report, fully browsable locally with sorting and much more:
Source file coverage details view:
Similarly to the usage with Test::Unit described above, the only thing you have to do is to add the simplecov config to the very top of your Cucumber/RSpec/whatever setup file.
Add the setup code to the top of features/support/env.rb
(for Cucumber) or spec/spec_helper.rb
(for RSpec).
Other test frameworks should work accordingly, whatever their setup file may be:
require 'simplecov'
SimpleCov.start 'rails'
You could even track what kind of code your UI testers are touching if you want to go overboard with things. SimpleCov does not care what kind of framework it is running in, it just looks at what code is being executed and generates a report about it.
For some frameworks and testing tools there are quirks and problems you might want to know about if you want to use SimpleCov with them. Here's an overview of the known ones:
Framework | Notes | Issue # |
---|---|---|
Test/Unit 2 |
Test Unit 2 used to mess with ARGV, leading to failure to detect the test process name in SimpleCov.
test-unit releases 2.4.3+ (Dec 11th, 2011) should have this problem resolved.
|
SimpleCov #45 & Test/Unit #12 |
Spork | Because of how Spork works internally (using preforking) there used to be trouble when using SimpleCov with it, but that has apparently been resolved with a specific configuration strategy. See this comment. | SimpleCov #42 |
parallel_tests | As of 0.8.0, SimpleCov should correctly recognize parallel_tests and supplement your test suite names with their corresponding test env numbers. Locking of the resultset cache should ensure no race conditions occur when results are merged. | SimpleCov #64 SimpleCov #185 |
Riot | A user has reported problems with the coverage report using the riot framework. If you experience similar trouble please follow up on the related Github issue. | SimpleCov #80 |
RubyMine | The RubyMine IDE has built-in support for SimpleCov's coverage reports, though you might need to explicitly set the output root using `SimpleCov.root('foo/bar/baz')` | SimpleCov #95 |
Configuration settings can be applied in three formats, which are completely equivalent:
- The most common way is to configure it directly in your start block:
SimpleCov.start do
some_config_option 'foo'
end
- You can also set all configuration options directly:
SimpleCov.some_config_option 'foo'
- If you do not want to start coverage immediately after launch or want to add additional configuration later on in a concise way, use:
SimpleCov.configure do
some_config_option 'foo'
end
Please check out the Configuration API documentation to find out what you can customize.
If you use SimpleCov to merge multiple test suite results (i.e. Test/Unit and Cucumber) into a single report, you'd normally have to
set up all your config options twice, once in test_helper.rb
and once in env.rb
.
To avoid this, you can place a file called .simplecov
in your project root. You can then just leave the require 'simplecov'
in each
test setup helper and move the SimpleCov.start
code with all your custom config options into .simplecov
:
# test/test_helper.rb
require 'simplecov'
# features/support/env.rb
require 'simplecov'
# .simplecov
SimpleCov.start 'rails' do
# any custom configs like groups and filters can be here at a central place
end
Filters can be used to remove selected files from your coverage data. By default, a filter is applied that removes all files OUTSIDE of your project's root directory - otherwise you'd end up with billions of coverage reports for source files in the gems you are using.
Of course you can define your own to remove things like configuration files, tests or whatever you don't need in your coverage report.
You can currently define a filter using either a String (that will then be Regexp-matched against each source file's path), a block or by passing in your own Filter class.
SimpleCov.start do
add_filter "/test/"
end
This simple string filter will remove all files that match "/test/" in their path.
SimpleCov.start do
add_filter do |source_file|
source_file.lines.count < 5
end
end
Block filters receive a SimpleCov::SourceFile instance and expect your block to return either true (if the file is to be removed from the result) or false (if the result should be kept). Please check out the RDoc for SimpleCov::SourceFile to learn about the methods available to you. In the above example, the filter will remove all files that have less than 5 lines of code.
class LineFilter < SimpleCov::Filter
def matches?(source_file)
source_file.lines.count < filter_argument
end
end
SimpleCov.add_filter LineFilter.new(5)
Defining your own filters is pretty easy: Just inherit from SimpleCov::Filter and define a method 'matches?(source_file)'. When running the filter, a true return value from this method will result in the removal of the given source_file. The filter_argument method is being set in the SimpleCov::Filter initialize method and thus is set to 5 in this example.
By default, SimpleCov filters everything outside of the SimpleCov.root
directory. However, sometimes you may want
to include coverage reports for things you include as a gem, for example a Rails Engine.
Here's an example by @lsaffie from #221 that shows how you can achieve just that:
SimpleCov.start :rails do
filters.clear # This will remove the :root_filter that comes via simplecov's defaults
add_filter do |src|
!(src.filename =~ /^#{SimpleCov.root}/) unless src.filename =~ /my_engine/
end
end
You can separate your source files into groups. For example, in a rails app, you'll want to have separate listings for Models, Controllers, Helpers, and Libs. Group definition works similar to Filters (and indeed also accepts custom filter classes), but source files end up in a group when the filter passes (returns true), as opposed to filtering results, which exclude files from results when the filter results in a true value.
Add your groups with:
SimpleCov.start do
add_group "Models", "app/models"
add_group "Controllers", "app/controllers"
add_group "Long files" do |src_file|
src_file.lines.count > 100
end
add_group "Short files", LineFilter.new(5) # Using the LineFilter class defined in Filters section above
end
Normally, you want to have your coverage analyzed across ALL of your test suites, right?
Simplecov automatically caches coverage results in your (coverage_path)/.resultset.json. Those results will then be automatically merged when generating the result, so when coverage is set up properly for cucumber and your unit / functional / integration tests, all of those test suites will be taken into account when building the coverage report.
There are two things to note here though:
Simplecov tries to guess the name of the currently running test suite based upon the shell command the tests are running on. This should work fine for Unit Tests, RSpec and Cucumber. If it fails, it will use the shell command that invoked the test suite as a command name.
If you have some non-standard setup and still want nicely labeled test suites, you have to give Simplecov a cue what the name of the currently running test suite is. You can do so by specifying SimpleCov.command_name in one test file that is part of your specific suite.
So, to customize the suite names on a Rails app (yeah, sorry for being Rails biased, but everyone knows what the structure of those projects is. You can apply this accordingly to the RSpecs in your Outlook-WebDAV-Calendar-Sync gem), you could do something like this:
# test/unit/some_test.rb
SimpleCov.command_name 'test:units'
# test/functionals/some_controller_test.rb
SimpleCov.command_name "test:functionals"
# test/integration/some_integration_test.rb
SimpleCov.command_name "test:integration"
# features/support/env.rb
SimpleCov.command_name "features"
Note that this only has to be invoked ONCE PER TEST SUITE, so even if you have 200 unit test files, specifying it in some_test.rb is fair enough.
simplecov-html prints the used test suites in the footer of the generated coverage report.
Of course, your cached coverage data is likely to become invalid at some point. Thus, result sets that are older than
SimpleCov.merge_timeout will not be used any more. By default, the timeout is 600 seconds (10 minutes), and you can
raise (or lower) it by specifying SimpleCov.merge_timeout 3600
(1 hour), or, inside a configure/start block, with
just "merge_timeout 3600".
You can deactivate merging altogether with SimpleCov.use_merging false
.
The Ruby STDLIB Coverage library that SimpleCov builds upon is very fast (i.e. on a ~10 min Rails test suite, the speed drop was only a couple seconds for me), and therefore it's SimpleCov's policy to just generate coverage every time you run your tests because it doesn't do your test speed any harm and you're always equipped with the latest and greatest coverage results.
Because of this, SimpleCov has no explicit built-in mechanism to run coverage only on demand.
However, you can still accomplish this very easily by introducing an ENV variable conditional into your SimpleCov setup block, like this:
SimpleCov.start if ENV["COVERAGE"]
Then, SimpleCov will only run if you execute your tests like this:
COVERAGE=true rake test
By default, Simplecov's only config assumption is that you only want coverage reports for files inside your project root. To save you from repetitive configuration, you can use predefined blocks of configuration, called 'profiles', or define your own.
You can then pass the name of the profile to be used as the first argument to SimpleCov.start. For example, simplecov comes bundled with a 'rails' profile. It looks somewhat like this:
SimpleCov.profiles.define 'rails' do
add_filter '/test/'
add_filter '/config/'
add_group 'Controllers', 'app/controllers'
add_group 'Models', 'app/models'
add_group 'Helpers', 'app/helpers'
add_group 'Libraries', 'lib'
end
As you can see, it's just a SimpleCov.configure block. In your test_helper.rb, launch simplecov with:
SimpleCov.start 'rails'
OR
SimpleCov.start 'rails' do
# additional config here
end
You can load additional profiles with the SimpleCov.load_profile('xyz') method. This allows you to build upon an existing profile and customize it so you can reuse it in unit tests and cucumber features, for example.
# lib/simplecov_custom_profile.rb
require 'simplecov'
SimpleCov.profiles.define 'myprofile' do
load_profile 'rails'
add_filter 'vendor' # Don't include vendored stuff
end
# features/support/env.rb
require 'simplecov_custom_profile'
SimpleCov.start 'myprofile'
# test/test_helper.rb
require 'simplecov_custom_profile'
SimpleCov.start 'myprofile'
You can define what simplecov should do when your test suite finishes by customizing the at_exit hook:
SimpleCov.at_exit do
SimpleCov.result.format!
end
Above is the default behaviour. Do whatever you like instead!
You can define the minimum coverage percentage expected. SimpleCov will return non-zero if unmet.
SimpleCov.minimum_coverage 90
You can define the maximum coverage drop percentage at once. SimpleCov will return non-zero if exceeded.
SimpleCov.maximum_coverage_drop 5
You can also entirely refuse dropping coverage between test runs:
SimpleCov.refuse_coverage_drop
You can use your own formatter with:
SimpleCov.formatter = SimpleCov::Formatter::HTMLFormatter
When calling SimpleCov.result.format!, it will be invoked with SimpleCov::Formatter::YourFormatter.new.format(result), "result" being an instance of SimpleCov::Result. Do whatever your wish with that!
If you want to use multiple result formats, as of SimpleCov 0.7.0 you can use the built-in MultiFormatter:
SimpleCov.formatter = SimpleCov::Formatter::MultiFormatter[
SimpleCov::Formatter::HTMLFormatter,
SimpleCov::Formatter::CSVFormatter,
]
Apart from the direct companion simplecov-html, there are other formatters available:
by Fernando Guillen
"The target of this formatter is to cheat on Hudson so I can use the Ruby metrics plugin with SimpleCov."
by Fernando Guillen
CSV formatter for SimpleCov code coverage tool for ruby 1.9+
by Judson Lester
Includes a formatter for Simplecov that emits a Vim script to mark up code files with coverage information.
A formatter that prints the coverage of the file under test when you run a single test file.
by Vicent Llongo
JSON formatter for SimpleCov
by Matt Hale
A formatter that generates a coverage badge for use in your project's readme using ImageMagick.
Only Ruby 1.9+ ships with the coverage library that SimpleCov depends upon. SimpleCov is built against various other Rubies, including Rubinius and JRuby, in Continuous Integration, but this happens only to ensure that SimpleCov does not make your test suite crash right now. Whether SimpleCov will support JRuby/Rubinius in the future depends solely on whether those Ruby interpreters add the coverage library.
SimpleCov is built in Continuous Integration on 1.8.7, ree, 1.9.2, 1.9.3.
Try coverband.
See the contributing guide.
Thanks to Aaron Patterson for the original idea for this!
Copyright (c) 2010-2013 Christoph Olszowka. See MIT-LICENSE for details.