CircleCI 2.0 - Merge parallel coverage results for CodeClimate

README.md

CircleCI 2.0 Parallel Builds and CodeClimate

Add the Ruby script to your repo, and add this snippet into your new circle.yml:

- deploy:
    name: Merge and copy coverage data
    command: bundle exec path/to/circle.rb

It will only work if the tests pass.

circle.rb

#!/usr/bin/env ruby
# originally based on https://gist.github.com/evanwhalen/f74879e0549b67eb17bb

require 'codeclimate-test-reporter'
require 'open-uri'

# ENV['PROJECT_NAME'] => 'github/github'
api_url = "https://circleci.com/api/v1.1/project/github/#{ENV['CIRCLE_PROJECT_USERNAME']}/#{ENV['CIRCLE_PROJECT_REPONAME']}/#{ENV['CIRCLE_BUILD_NUM']}/artifacts?circle-token=#{ENV['CIRCLE_TOKEN']}"

artifacts = open(api_url)

coverage_dir = '/tmp/coverage'

SimpleCov.coverage_dir(coverage_dir)

JSON.load(artifacts)
    .map { |artifact| JSON.load(open("#{artifact['url']}?circle-token=#{ENV['CIRCLE_TOKEN']}")) }
    .each_with_index do |resultset, i|
      resultset.each do |_, data|
        result = SimpleCov::Result.from_hash(['command', i].join => data)
        SimpleCov::ResultMerger.store_result(result)
      end
    end

merged_result = SimpleCov::ResultMerger.merged_result
merged_result.command_name = 'RSpec'

CodeClimate::TestReporter.run(merged_result.to_hash)

Here is an updated gist covering this technique and another technique(using workflows) to generate coverage reports locally. It also generates html report.
Happy coding!