Merging simplecov resultsets

coverage_merger.rb

# frozen_string_literal: true

module CoverageMerger
  def self.merge(directories:)
    require 'json'
    require 'simplecov'

    # Simplecov generates a report on exit by default
    # We are doing this manually with merged resultsets
    SimpleCov.at_exit {}
    # SimpleCov.filters.clear

    coverage_results = []
    directories.each do |directory|
      puts "Loading #{directory}"

      # load json results from coverage folder
      file = File.join(directory, '.resultset.json')
      file_results = JSON.parse(File.read(file))

      # parse results from coverage file to array
      file_results.each do |command, data|
        result = SimpleCov::Result.from_hash(command => data)
        coverage_results << result
      end
    end

    puts 'Merging results'
    # merge results from array to results object
    merged_results = SimpleCov::ResultMerger.merge_results(*coverage_results)

    puts 'Printing merged results'
    # output the merged resultset to .resultset.json
    SimpleCov::ResultMerger.store_result(merged_results)

    # output the total coverage percentage to .last_run.json
    SimpleCov.write_last_run(merged_results.covered_percent)

    # output the merged results to index.html
    merged_results.format!
  end
end