Cucumber::Blanket
Works to extract accumulated Blanket.js coverage data from the browser from a Cucumber environment. Accumulated, in this context, means that coverage data is accumulated from scenario to scenario, in an additive fashion.
Installation
Add this line to your application's Gemfile:
gem 'cucumber-blanket'
And then execute:
$ bundle
Or install it yourself as:
$ gem install cucumber-blanket
Usage
You should be using Cucumber
Require this gem at the top of features/support/env.rb
or before using it.
require 'cucumber/blanket'
Install blanket.js
Two javascript files are bundled;
- blanket.js -- the library itself
- cucumber-blanket.js -- a very simple modification
These two files must be loaded on the front-end --- be sure to follow
blanket.js's specifications (you must add the attribute data-cover
to
any scripts you want blanket.js to instrument)
cucumber-blanket.js initiates a coverage report session -- you are expected to complete the session from the Cucumber side. In this design, we make use of Cucumber's After hook:
After do |scenario|
# Grab code coverage from the frontend
# Currently this adds >1 second to every scenario, but it's worth it
Cucumber::Blanket.extract_from page
end
Of course every scenario will touch on different parts of your code, as such Cucumber::Blanket OR's the lines. In other words, if line 10 of File A was covered in Scenario X, but not in Scenario Y, line 10 is considered covered when Cucumber has finished running.
Finally, to gain access to the accumulated coverage data, you can use the shorthand Cucumber::Blanket.files
:
after_exit do
covdata = # do something with it
File.open("tmp/coverage.json", "w") do |file|
file.write Cucumber::Blanket.files.to_json
# writes out JSON of this form of ruby hash:
# => {"http://127.0.0.1:32344/js/collections/assets.js"=>
# [3, 3, 3, nil, 3, nil, nil, nil, 0, 0, nil, 0, nil, nil, nil, nil, 0, 0]}
# {filename=>[lineCov,lineCov,lineCov]}
# At this stage you can fetch the files and create a nice HTML report, etc
end
end
I have both of these in my features/support/hooks.rb
file. As far as doing something useful
with the coverage data, that's left up to the user, another gem, or maybe blanket.js itself from Node.js.
Other Features
Percent
You can use Cucumber::Blanket.percent
to get a float value of coverage of known lines of code.
For example, you can do something like this to watch coverage increasing on every scenario:
After do |scenario|
old_pct = Cucumber::Blanket.percent
Cucumber::Blanket.extract_from page
current_pct = Cucumber::Blanket.percent
pct_added = current_pct - old_pct
STDOUT.puts "Coverage: #{current_pct}% (+#{pct_added}%)"
end
at_exit do
STDOUT.puts "Final coverage: #{Cucumber::Blanket.percent}%"
end
Write HTML Report
After you've captured some coverage data, you can create an HTML report like so:
Cucumber::Blanket.write_html_report File.join(File.dirname(__FILE__), '../../coverage.html')
I like to put this in after_exit
in my Cucumber hooks.rb
file
Dev Notes
To create the spec/fixtures/simple.json
with new real data, add this line
to Cucumber::Blanket#extract_from once you have a handle to page_data:
File.open("tmp/out.json", 'w'){|f| f.write page_data.to_json}
Run it through jsbeautifier and add it
Contributing
- Fork it
- Create your feature branch (
git checkout -b my-new-feature
) - Commit your changes (
git commit -am 'Add some feature'
) - Push to the branch (
git push origin my-new-feature
) - Create new Pull Request