Merge coverage reports from parallel circle test containers

merge_coverage.rb

#!/usr/bin/env ruby
# frozen_string_literal: true

require 'simplecov'
require 'simplecov-lcov'

puts('Merging coverage results from parallel CircleCI tests containers into a single LCOV report...')

results = []
Dir['/home/circleci/rspec/*.resultset.json'].each do |path|
  resultset = JSON.parse(File.read(path))
  resultset.each do |_, data|
    cmd = File.basename(path)
    results << SimpleCov::Result.from_hash(cmd => data)
  end
  print '.'
end
puts

merged_result = SimpleCov::ResultMerger.merge_results(*results)

SimpleCov::Formatter::LcovFormatter.config.report_with_single_file = true
SimpleCov::Formatter::LcovFormatter.config.single_report_path = ARGV[0] || 'coverage.lcov'
SimpleCov::Formatter::LcovFormatter.new.format(merged_result)

puts("Done! LCOV saved to #{SimpleCov::Formatter::LcovFormatter.config.single_report_path}")