Coverage::Helpers

This gem provides some helper methods to manipulate the coverage results measured by Coverage.result of the coverage.so library.

Currently, the following methods are available:

• Coverage::Helpers.merge(*covs): Sum up all coverage results.
• Coverage::Helpers.diff(cov1, cov2): Extract the coverage results that is covered by cov1 but not covered by cov2.
• Coverage::Helpers.sanitize(cov): Make the coverage result able to Marshal#dump. (See the Notes section.)
• Coverage::Helpers.save(filename, cov): Save the coverage result to a file.
• Coverage::Helpers.load(filename): Load the coverage result from a file.
• Coverage::Helpers.to_lcov_info(cov): Translate the result into LCOV info format.

Add this line to your application's Gemfile:

gem 'coverage-helpers'

And then execute:

$ bundle

Or install it yourself as:

$ gem install coverage-helpers

Here is an example:

$ cd example
$ ruby measure.rb -o cov1.dat -l cov1.info -- file.rb 1
$ genhtml --branch-coverage cov1.info -o cov1-lcov
$ open cov1-lcov/index.html

Note that genhtml is an executable of LCOV that visualizes LCOV info data by HTML view.

You can merge the coverage results of multiple runs:

$ ruby measure.rb -o cov1.dat -l cov1.info -- file.rb 1
$ ruby measure.rb -o cov2.dat -l cov2.info -a cov1.dat -- file.rb 2
$ genhtml --branch-coverage cov2.info -o cov2-lcov
$ open cov2-lcov/index.html

You can also check the newly covered code:

$ ruby measure.rb -o cov1.dat -l cov1.info -- file.rb 1
$ ruby measure.rb -o cov2.dat -l cov2.info -b cov1.dat -- file.rb 2
$ genhtml --branch-coverage cov2.info -o cov2-lcov
$ open cov2-lcov/index.html

See example/measure.rb in detail.

There are two formats of Coverage.result. One is an old format, which Ruby 2.4 or before returns. It can contain only line coverage. The other is a new format, which Ruby 2.5 or later generates. It can contain line, branch, and method coverage. All methods of this gem support both format.

Method coverage data contains a class defined a measured method. The class may be a singleton class, which Marshal.dump cannot handle. This is why this gem provides sanitize. The method replaces all singleton classes with its string representation by using to_s.

Bug reports and pull requests are welcome on GitHub at https://github.com/mame/coverage-helpers.

The gem is available as open source under the terms of the MIT License.