Rspec file benchmark rake task

rspec_benchmark.rake

# frozen_string_literal: true

desc 'Run an RSpec file multiple times and report timing statistics. Usage: rake rspec_benchmark[spec/path/to/file,5]'
task :rspec_benchmark, [:file, :runs] do |_t, args|
  file = args[:file]
  runs = args[:runs]&.to_i

  if file.nil? || file.empty?
    puts "Usage: rake rspec_benchmark[spec/path/to/file,number_of_runs]"
    exit 1
  end

  unless File.exist?(file)
    puts "File not found: #{file}"
    exit 1
  end

  if runs.nil? || runs < 1
    puts "Number of runs must be at least 1."
    exit 1
  end

  times = []

  runs.times do |i|
    puts "\n#{'=' * 60}"
    puts "Run #{i + 1} of #{runs}"
    puts '=' * 60

    output = `bundle exec rspec #{file} 2>&1`
    puts output

    if (match = output.match(/Finished in (\d+\.?\d*) seconds?/))
      duration = match[1].to_f
      times << duration
      puts ">> Run #{i + 1} completed in #{duration}s"
    else
      puts ">> Run #{i + 1}: Could not parse timing from output."
    end
  end

  if times.empty?
    puts "\nNo timing data collected."
    exit 1
  end

  sorted = times.sort
  sum = sorted.sum
  count = sorted.length
  mean = sum / count
  median = if count.odd?
             sorted[count / 2]
           else
             (sorted[(count / 2) - 1] + sorted[count / 2]) / 2.0
           end
  range = sorted.last - sorted.first

  frequency = sorted.map { |t| t.round(1) }.tally
  max_freq = frequency.values.max
  modes = frequency.select { |_, v| v == max_freq }.keys

  puts "\n#{'=' * 60}"
  puts 'RESULTS'
  puts '=' * 60
  times.each_with_index do |t, i|
    puts "  Run #{i + 1}: #{t.round(4)}s"
  end
  puts '-' * 40
  puts "  Mean:   #{mean.round(4)}s"
  puts "  Median: #{median.round(4)}s"
  puts "  Mode:   #{modes.map { |m| "#{m}s" }.join(', ')} (rounded to 0.1s, appeared #{max_freq}x)"
  puts "  Range:  #{range.round(4)}s (#{sorted.first.round(4)}s – #{sorted.last.round(4)}s)"
  puts '=' * 60
end