common_stack.rb

require 'minitest'

module Minitest
  def self.plugin_common_init options
    reporter << CommonTests.new
  end
end

class CommonTests < Minitest::AbstractReporter
  def initialize
    @results = []
  end

  def record result
    @results << result unless result.passed? || result.skipped?
  end

  def report
    results = @results.group_by { |result|
      result.failures.map { |e| e.backtrace }
    }

    print "#" * 20
    print " COMMON STACK "
    puts "#" * 20
    x = results.map do |stack,rs|
      rs.each do |result|
        "\n%3d) %s" % [1, result] # fixme
      end
    end.join("\n") + "\n"
    puts x
  end
end

Minitest.extensions << 'common'