support concurrent btest execution

* `-j` option for concurrent test with threads
  * `-jN` uses N threads
  * `-j` uses nproc/2 threads
* Introduce `BT` struct to manage configurations
* Introduce `Assertion` to manage all assertions
* Remove all toplevel instance variables
* Show elapsed seconds at last

```
$ time make btest
...
real    0m37.319s
user    0m26.221s
sys     0m16.534s

$ time make btest TESTOPTS=-j
...
real    0m11.812s
user    0m36.667s
sys     0m21.872s
```

1 files changed, 459 insertions, 304 deletions

diff --git a/bootstraptest/runner.rb b/bootstraptest/runner.rb
index a4101594f1..1be0d677c0 100755
--- a/bootstraptest/runner.rb
+++ b/bootstraptest/runner.rb
@@ -8,6 +8,8 @@
 # Never use Ruby extensions in this file.
 # Maintain Ruby 1.8 compatibility for now
 
+$start_time = Time.now
+
 begin
   require 'fileutils'
   require 'tmpdir'
@@ -58,24 +60,44 @@ if !Dir.respond_to?(:mktmpdir)
   end
 end
 
+# Configuration
+BT = Struct.new(:ruby,
+                :verbose,
+                :color,
+                :tty,
+                :quiet,
+                :wn,
+                :progress,
+                :progress_bs,
+                :passed,
+                :failed,
+                :reset,
+                :columns,
+                :width,
+                ).new
+
+BT_STATE = Struct.new(:count, :error).new
+
 def main
-  @ruby = File.expand_path('miniruby')
-  @verbose = false
+  BT.ruby = File.expand_path('miniruby')
+  BT.verbose = false
   $VERBOSE = false
   $stress = false
-  @color = nil
-  @tty = nil
-  @quiet = false
+  BT.color = nil
+  BT.tty = nil
+  BT.quiet = false
+  BT.wn = 1
   dir = nil
   quiet = false
   tests = nil
   ARGV.delete_if {|arg|
     case arg
     when /\A--ruby=(.*)/
-      @ruby = $1
-      @ruby.gsub!(/^([^ ]*)/){File.expand_path($1)}
-      @ruby.gsub!(/(\s+-I\s*)((?!(?:\.\/)*-(?:\s|\z))\S+)/){$1+File.expand_path($2)}
-      @ruby.gsub!(/(\s+-r\s*)(\.\.?\/\S+)/){$1+File.expand_path($2)}
+      ruby = $1
+      ruby.gsub!(/^([^ ]*)/){File.expand_path($1)}
+      ruby.gsub!(/(\s+-I\s*)((?!(?:\.\/)*-(?:\s|\z))\S+)/){$1+File.expand_path($2)}
+      ruby.gsub!(/(\s+-r\s*)(\.\.?\/\S+)/){$1+File.expand_path($2)}
+      BT.ruby = ruby
       true
     when /\A--sets=(.*)/
       tests = Dir.glob("#{File.dirname($0)}/test_{#{$1}}*.rb").sort
@@ -88,18 +110,26 @@ def main
       $stress = true
     when /\A--color(?:=(?:always|(auto)|(never)|(.*)))?\z/
       warn "unknown --color argument: #$3" if $3
-      @color = $1 ? nil : !$2
+      BT.color = color = $1 ? nil : !$2
       true
     when /\A--tty(=(?:yes|(no)|(.*)))?\z/
       warn "unknown --tty argument: #$3" if $3
-      @tty = !$1 || !$2
+      BT.tty = !$1 || !$2
       true
     when /\A(-q|--q(uiet))\z/
       quiet = true
-      @quiet = true
+      BT.quiet = true
+      true
+    when /\A-j(\d+)?/
+      wn = $1.to_i
+      if wn <= 0
+        require 'etc'
+        wn = [Etc.nprocessors / 2, 1].max
+      end
+      BT.wn = wn
       true
     when /\A(-v|--v(erbose))\z/
-      @verbose = true
+      BT.verbose = true
     when /\A(-h|--h(elp)?)\z/
       puts(<<-End)
 Usage: #{File.basename($0, '.*')} --ruby=PATH [--sets=NAME,NAME,...]
@@ -128,15 +158,16 @@ End
   tests = Dir.glob("#{File.dirname($0)}/test_*.rb").sort if tests.empty?
   pathes = tests.map {|path| File.expand_path(path) }
 
-  @progress = %w[- \\ | /]
-  @progress_bs = "\b" * @progress[0].size
-  @tty = $stderr.tty? if @tty.nil?
-  case @color
+  BT.progress = %w[- \\ | /]
+  BT.progress_bs = "\b" * BT.progress[0].size
+  BT.tty = $stderr.tty? if BT.tty.nil?
+
+  case BT.color
   when nil
-    @color = @tty && /dumb/ !~ ENV["TERM"]
+    BT.color = BT.tty && /dumb/ !~ ENV["TERM"]
   end
-  @tty &&= !@verbose
-  if @color
+  BT.tty &&= !BT.verbose
+  if BT.color
     # dircolors-like style
     colors = (colors = ENV['TEST_COLORS']) ? Hash[colors.scan(/(\w+)=([^:\n]*)/)] : {}
     begin
@@ -145,14 +176,14 @@ End
       end
     rescue
     end
-    @passed = "\e[;#{colors["pass"] || "32"}m"
-    @failed = "\e[;#{colors["fail"] || "31"}m"
-    @reset = "\e[m"
+    BT.passed = "\e[;#{colors["pass"] || "32"}m"
+    BT.failed = "\e[;#{colors["fail"] || "31"}m"
+    BT.reset = "\e[m"
   else
-    @passed = @failed = @reset = ""
+    BT.passed = BT.failed = BT.reset = ""
   end
   unless quiet
-    puts Time.now
+    puts $start_time
     if defined?(RUBY_DESCRIPTION)
       puts "Driver is #{RUBY_DESCRIPTION}"
     elsif defined?(RUBY_PATCHLEVEL)
@@ -160,289 +191,473 @@ End
     else
       puts "Driver is ruby #{RUBY_VERSION} (#{RUBY_RELEASE_DATE}) [#{RUBY_PLATFORM}]"
     end
-    puts "Target is #{`#{@ruby} -v`.chomp}"
+    puts "Target is #{`#{BT.ruby} -v`.chomp}"
     puts
     $stdout.flush
   end
 
-  in_temporary_working_directory(dir) {
+  in_temporary_working_directory(dir) do
     exec_test pathes
-  }
+  end
 end
 
 def erase(e = true)
-  if e and @columns > 0 and @tty and !@verbose
+  if e and BT.columns > 0 and BT.tty and !BT.verbose
     "\e[1K\r"
   else
     ""
   end
 end
 
-def exec_test(pathes)
-  @count = 0
-  @error = 0
-  @errbuf = []
-  @location = nil
-  @columns = 0
-  @width = pathes.map {|path| File.basename(path).size}.max + 2
+def load_test pathes
   pathes.each do |path|
-    @basename = File.basename(path)
-    unless @quiet
-      $stderr.printf("%s%-*s ", erase(@quiet), @width, @basename)
-      $stderr.flush
-    end
-    @columns = @width + 1
-    $stderr.puts if @verbose
-    count = @count
-    error = @error
     load File.expand_path(path)
-    if @tty
-      if @error == error
-        msg = "PASS #{@count-count}"
-        @columns += msg.size - 1
-        $stderr.print "#{@progress_bs}#{@passed}#{msg}#{@reset}" unless @quiet
+  end
+end
+
+def concurrent_exec_test
+  aq = Queue.new
+  rq = Queue.new
+
+  ts = BT.wn.times.map do
+    Thread.new do
+      while as = aq.pop
+        as.call
+        rq << as
+      end
+    ensure
+      rq << nil
+    end
+  end
+
+  Assertion.all.to_a.shuffle.each do |path, assertions|
+    assertions.each do |as|
+      aq << as
+    end
+  end
+
+  $stderr.print ' ' unless BT.quiet
+  aq.close
+  i = 1
+  term_wn = 0
+  begin
+    while BT.wn != term_wn
+      if r = rq.pop
+        case
+        when BT.quiet
+        when BT.tty
+          $stderr.print "#{BT.progress_bs}#{BT.progress[(i+=1) % BT.progress.size]}"
+        else
+          $stderr.print '.'
+        end
       else
-        msg = "FAIL #{@error-error}/#{@count-count}"
-        $stderr.print "#{@progress_bs}#{@failed}#{msg}#{@reset}"
-        @columns = 0
+        term_wn += 1
+      end
+    end
+  ensure
+    ts.each(&:kill)
+    ts.each(&:join)
+  end
+end
+
+def exec_test(pathes)
+  # setup
+  load_test pathes
+  BT_STATE.count = 0
+  BT_STATE.error = 0
+  BT.columns = 0
+  BT.width = pathes.map {|path| File.basename(path).size}.max + 2
+
+  # execute tests
+  if BT.wn > 1
+    concurrent_exec_test if BT.wn > 1
+  else
+    prev_basename = nil
+    Assertion.all.each do |basename, assertions|
+      if !BT.quiet && basename != prev_basename
+        prev_basename = basename
+        $stderr.printf("%s%-*s ", erase(BT.quiet), BT.width, basename)
+        $stderr.flush
+      end
+      BT.columns = BT.width + 1
+      $stderr.puts if BT.verbose
+      count = BT_STATE.count
+      error = BT_STATE.error
+
+      assertions.each do |assertion|
+        BT_STATE.count += 1
+        assertion.call
+      end
+
+      if BT.tty
+        if BT_STATE.error == error
+          msg = "PASS #{BT_STATE.count-count}"
+          BT.columns += msg.size - 1
+          $stderr.print "#{BT.progress_bs}#{BT.passed}#{msg}#{BT.reset}" unless BT.quiet
+        else
+          msg = "FAIL #{BT_STATE.error-error}/#{BT_STATE.count-count}"
+          $stderr.print "#{BT.progress_bs}#{BT.failed}#{msg}#{BT.reset}"
+          BT.columns = 0
+        end
       end
+      $stderr.puts if !BT.quiet and (BT.tty or BT_STATE.error == error)
     end
-    $stderr.puts if !@quiet and (@tty or @error == error)
   end
-  $stderr.print(erase) if @quiet
-  @errbuf.each do |msg|
+
+  # show results
+  unless BT.quiet
+    $stderr.puts(erase)
+
+    sec = Time.now - $start_time
+    $stderr.puts "Finished in #{'%.2f' % sec} sec\n\n" if Assertion.count > 0
+  end
+
+  Assertion.errbuf.each do |msg|
     $stderr.puts msg
   end
 
-  out = @quiet ? $stdout : $stderr
+  out = BT.quiet ? $stdout : $stderr
 
-  if @error == 0
-    if @count == 0
-      out.puts "No tests, no problem" unless @quiet
+  if BT_STATE.error == 0
+    if Assertion.count == 0
+      out.puts "No tests, no problem" unless BT.quiet
     else
-      out.puts "#{@passed}PASS#{@reset} all #{@count} tests"
+      out.puts "#{BT.passed}PASS#{BT.reset} all #{Assertion.count} tests"
     end
-    exit true
+    true
   else
-    $stderr.puts "#{@failed}FAIL#{@reset} #{@error}/#{@count} tests failed"
-    exit false
+    $stderr.puts "#{BT.failed}FAIL#{BT.reset} #{BT_STATE.error}/#{BT_STATE.count} tests failed"
+    false
   end
 end
 
-def show_progress(message = '')
-  if @quiet
-    # do nothing
-  elsif @verbose
-    $stderr.print "\##{@count} #{@location} "
-  elsif @tty
-    $stderr.print "#{@progress_bs}#{@progress[@count % @progress.size]}"
-  end
-  t = Time.now if @verbose
-  faildesc, errout = with_stderr {yield}
-  t = Time.now - t if @verbose
-  if !faildesc
-    if @quiet
-      # do nothing
-    elsif @tty
-      $stderr.print "#{@progress_bs}#{@progress[@count % @progress.size]}"
-    elsif @verbose
-      $stderr.printf(". %.3f\n", t)
-    else
-      $stderr.print '.'
-    end
+def target_platform
+  if BT.ruby
+    `#{BT.ruby} --disable-gems -e 'print RUBY_PLATFORM'`
   else
-    $stderr.print "#{@failed}F"
-    $stderr.printf(" %.3f", t) if @verbose
-    $stderr.print @reset
-    $stderr.puts if @verbose
-    error faildesc, message
-    unless errout.empty?
-      $stderr.print "#{@failed}stderr output is not empty#{@reset}\n", adjust_indent(errout)
+    RUBY_PLATFORM
+  end
+end
+
+class Assertion < Struct.new(:src, :path, :lineno, :proc)
+  @count = 0
+  @all = Hash.new{|h, k| h[k] = []}
+  @errbuf = []
+
+  class << self
+    attr_reader :count, :errbuf
+
+    def all
+      @all
     end
-    if @tty and !@verbose
-      $stderr.printf("%-*s%s", @width, @basename, @progress[@count % @progress.size])
+
+    def add as
+      @all[as.path] << as
+      as.id = (@count += 1)
     end
   end
-rescue Interrupt
-  $stderr.puts "\##{@count} #{@location}"
-  raise
-rescue Exception => err
-  $stderr.print 'E'
-  $stderr.puts if @verbose
-  error err.message, message
-ensure
-  begin
-    check_coredump
-  rescue CoreDumpError => err
+
+  attr_accessor :id
+  attr_reader :err, :category
+
+  def initialize(*args)
+    super
+    self.class.add self
+    @category = self.path.match(/test_(.+)\.rb/)[1]
+  end
+
+  def call
+    self.proc.call self
+  end
+
+  def assert_check(message = '', opt = '', **argh)
+    show_progress(message) {
+      result = get_result_string(opt, **argh)
+      yield(result)
+    }
+  end
+
+  def with_stderr
+    out = err = nil
+    r, w = IO.pipe
+    @err = w
+    err_reader = Thread.new{ r.read }
+
+    begin
+      out = yield
+    ensure
+      w.close
+      err = err_reader.value
+      r.close rescue nil
+    end
+
+    return out, err
+  end
+
+  def show_error(msg, additional_message)
+    msg = "#{BT.failed}\##{self.id} #{self.path}:#{self.lineno}#{BT.reset}: #{msg}  #{additional_message}"
+    if BT.tty
+      $stderr.puts "#{erase}#{msg}"
+    else
+      Assertion.errbuf << msg
+    end
+    BT_STATE.error += 1
+  end
+
+
+  def show_progress(message = '')
+    if BT.quiet || BT.wn > 1
+      # do nothing
+    elsif BT.verbose
+      $stderr.print "\##{@id} #{self.path}:#{self.lineno} "
+    elsif BT.tty
+      $stderr.print "#{BT.progress_bs}#{BT.progress[BT_STATE.count % BT.progress.size]}"
+    end
+
+    t = Time.now if BT.verbose
+    faildesc, errout = with_stderr {yield}
+    t = Time.now - t if BT.verbose
+
+    if !faildesc
+      # success
+      if BT.quiet || BT.wn > 1
+        # do nothing
+      elsif BT.tty
+        $stderr.print "#{BT.progress_bs}#{BT.progress[BT_STATE.count % BT.progress.size]}"
+      elsif BT.verbose
+        $stderr.printf(". %.3f\n", t)
+      else
+        $stderr.print '.'
+      end
+    else
+      $stderr.print "#{BT.failed}F"
+      $stderr.printf(" %.3f", t) if BT.verbose
+      $stderr.print BT.reset
+      $stderr.puts if BT.verbose
+      show_error faildesc, message
+      unless errout.empty?
+        $stderr.print "#{BT.failed}stderr output is not empty#{BT.reset}\n", adjust_indent(errout)
+      end
+
+      if BT.tty and !BT.verbose and BT.wn == 1
+        $stderr.printf("%-*s%s", BT.width, path, BT.progress[BT_STATE.count % BT.progress.size])
+      end
+    end
+  rescue Interrupt
+    $stderr.puts "\##{@id} #{path}:#{lineno}"
+    raise
+  rescue Exception => err
     $stderr.print 'E'
-    $stderr.puts if @verbose
-    error err.message, message
+    $stderr.puts if BT.verbose
+    show_error err.message, message
+  ensure
+    begin
+      check_coredump
+    rescue CoreDumpError => err
+      $stderr.print 'E'
+      $stderr.puts if BT.verbose
+      show_error err.message, message
+      cleanup_coredump
+    end
   end
-end
 
-def target_platform
-  if @ruby
-    `#{@ruby} --disable-gems -e 'print RUBY_PLATFORM'`
-  else
-    RUBY_PLATFORM
+  def get_result_string(opt = '', **argh)
+    if BT.ruby
+      filename = make_srcfile(**argh)
+      begin
+        kw = self.err ? {err: self.err} : {}
+        out = IO.popen("#{BT.ruby} -W0 #{opt} #{filename}", **kw)
+        pid = out.pid
+        out.read.tap{ Process.waitpid(pid); out.close }
+      ensure
+        raise Interrupt if $? and $?.signaled? && $?.termsig == Signal.list["INT"]
+
+        begin
+          Process.kill :KILL, pid
+        rescue Errno::ESRCH
+          # OK
+        end
+      end
+    else
+      eval(src).to_s
+    end
   end
-end
 
-def show_limit(testsrc, opt = '', **argh)
-  result = get_result_string(testsrc, opt, **argh)
-  if @tty and @verbose
-    $stderr.puts ".{#@reset}\n#{erase}#{result}"
-  else
-    @errbuf.push result
+  def make_srcfile(frozen_string_literal: nil)
+    filename = "bootstraptest.#{self.path}_#{self.lineno}_#{self.id}.rb"
+    File.open(filename, 'w') {|f|
+      f.puts "#frozen_string_literal:true" if frozen_string_literal
+      f.puts "GC.stress = true" if $stress
+      f.puts "print(begin; #{self.src}; end)"
+    }
+    filename
   end
 end
 
-def assert_check(testsrc, message = '', opt = '', **argh)
-  show_progress(message) {
-    result = get_result_string(testsrc, opt, **argh)
-    yield(result)
-  }
+def add_assertion src, pr
+  loc = caller_locations(2, 1).first
+  lineno = loc.lineno
+  path = File.basename(loc.path)
+
+  Assertion.new(src, path, lineno, pr)
 end
 
 def assert_equal(expected, testsrc, message = '', opt = '', **argh)
-  newtest
-  assert_check(testsrc, message, opt, **argh) {|result|
-    if expected == result
-      nil
-    else
-      desc = "#{result.inspect} (expected #{expected.inspect})"
-      pretty(testsrc, desc, result)
-    end
-  }
+  add_assertion testsrc, -> as do
+    as.assert_check(message, opt, **argh) {|result|
+      if expected == result
+        nil
+      else
+        desc = "#{result.inspect} (expected #{expected.inspect})"
+        pretty(testsrc, desc, result)
+      end
+    }
+  end
 end
 
 def assert_match(expected_pattern, testsrc, message = '')
-  newtest
-  assert_check(testsrc, message) {|result|
-    if expected_pattern =~ result
-      nil
-    else
-      desc = "#{expected_pattern.inspect} expected to be =~\n#{result.inspect}"
-      pretty(testsrc, desc, result)
-    end
-  }
+  add_assertion testsrc, -> as do
+    as.assert_check(message) {|result|
+      if expected_pattern =~ result
+        nil
+      else
+        desc = "#{expected_pattern.inspect} expected to be =~\n#{result.inspect}"
+        pretty(testsrc, desc, result)
+      end
+    }
+  end
 end
 
 def assert_not_match(unexpected_pattern, testsrc, message = '')
-  newtest
-  assert_check(testsrc, message) {|result|
-    if unexpected_pattern !~ result
-      nil
-    else
-      desc = "#{unexpected_pattern.inspect} expected to be !~\n#{result.inspect}"
-      pretty(testsrc, desc, result)
-    end
-  }
+  add_assertion testsrc, -> as do
+    as.assert_check(message) {|result|
+      if unexpected_pattern !~ result
+        nil
+      else
+        desc = "#{unexpected_pattern.inspect} expected to be !~\n#{result.inspect}"
+        pretty(testsrc, desc, result)
+      end
+    }
+  end
 end
 
 def assert_valid_syntax(testsrc, message = '')
-  newtest
-  assert_check(testsrc, message, '-c') {|result|
-    result if /Syntax OK/ !~ result
-  }
+  add_assertion testsrc, -> as do
+    as.assert_check(message, '-c') {|result|
+      result if /Syntax OK/ !~ result
+    }
+  end
 end
 
 def assert_normal_exit(testsrc, *rest, timeout: nil, **opt)
-  newtest
-  message, ignore_signals = rest
-  message ||= ''
-  show_progress(message) {
-    faildesc = nil
-    filename = make_srcfile(testsrc)
-    old_stderr = $stderr.dup
-    timeout_signaled = false
-    begin
-      $stderr.reopen("assert_normal_exit.log", "w")
-      io = IO.popen("#{@ruby} -W0 #{filename}")
-      pid = io.pid
-      th = Thread.new {
-        io.read
-        io.close
-        $?
-      }
-      if !th.join(timeout)
-        Process.kill :KILL, pid
-        timeout_signaled = true
-      end
-      status = th.value
-    ensure
-      $stderr.reopen(old_stderr)
-      old_stderr.close
-    end
-    if status && status.signaled?
-      signo = status.termsig
-      signame = Signal.list.invert[signo]
-      unless ignore_signals and ignore_signals.include?(signame)
-        sigdesc = "signal #{signo}"
-        if signame
-          sigdesc = "SIG#{signame} (#{sigdesc})"
-        end
-        if timeout_signaled
-          sigdesc << " (timeout)"
+  add_assertion testsrc, -> as do
+    message, ignore_signals = rest
+    message ||= ''
+    as.show_progress(message) {
+      faildesc = nil
+      filename = as.make_srcfile
+      timeout_signaled = false
+      logfile = "assert_normal_exit.#{as.path}.#{as.lineno}.log"
+
+      begin
+        err = open(logfile, "w")
+        io = IO.popen("#{BT.ruby} -W0 #{filename}", err: err)
+        pid = io.pid
+        th = Thread.new {
+          io.read
+          io.close
+          $?
+        }
+        if !th.join(timeout)
+          Process.kill :KILL, pid
+          timeout_signaled = true
         end
-        faildesc = pretty(testsrc, "killed by #{sigdesc}", nil)
-        stderr_log = File.read("assert_normal_exit.log")
-        if !stderr_log.empty?
-          faildesc << "\n" if /\n\z/ !~ faildesc
-          stderr_log << "\n" if /\n\z/ !~ stderr_log
-          stderr_log.gsub!(/^.*\n/) { '| ' + $& }
-          faildesc << stderr_log
+        status = th.value
+      ensure
+        err.close
+      end
+      if status && status.signaled?
+        signo = status.termsig
+        signame = Signal.list.invert[signo]
+        unless ignore_signals and ignore_signals.include?(signame)
+          sigdesc = "signal #{signo}"
+          if signame
+            sigdesc = "SIG#{signame} (#{sigdesc})"
+          end
+          if timeout_signaled
+            sigdesc << " (timeout)"
+          end
+          faildesc = pretty(testsrc, "killed by #{sigdesc}", nil)
+          stderr_log = File.read(logfile)
+          if !stderr_log.empty?
+            faildesc << "\n" if /\n\z/ !~ faildesc
+            stderr_log << "\n" if /\n\z/ !~ stderr_log
+            stderr_log.gsub!(/^.*\n/) { '| ' + $& }
+            faildesc << stderr_log
+          end
         end
       end
-    end
-    faildesc
-  }
+      faildesc
+    }
+  end
 end
 
 def assert_finish(timeout_seconds, testsrc, message = '')
-  if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
-    timeout_seconds *= 3
-  end
-  newtest
-  show_progress(message) {
-    faildesc = nil
-    filename = make_srcfile(testsrc)
-    io = IO.popen("#{@ruby} -W0 #{filename}")
-    pid = io.pid
-    waited = false
-    tlimit = Time.now + timeout_seconds
-    diff = timeout_seconds
-    while diff > 0
-      if Process.waitpid pid, Process::WNOHANG
-        waited = true
-        break
-      end
-      if io.respond_to?(:read_nonblock)
-        if IO.select([io], nil, nil, diff)
-          begin
-            io.read_nonblock(1024)
-          rescue Errno::EAGAIN, IO::WaitReadable, EOFError
-            break
-          end while true
+  add_assertion testsrc, -> as do
+    if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+      timeout_seconds *= 3
+    end
+
+    as.show_progress(message) {
+      faildesc = nil
+      filename = as.make_srcfile
+      io = IO.popen("#{BT.ruby} -W0 #{filename}", err: as.err)
+      pid = io.pid
+      waited = false
+      tlimit = Time.now + timeout_seconds
+      diff = timeout_seconds
+      while diff > 0
+        if Process.waitpid pid, Process::WNOHANG
+          waited = true
+          break
         end
-      else
-        sleep 0.1
+        if io.respond_to?(:read_nonblock)
+          if IO.select([io], nil, nil, diff)
+            begin
+              io.read_nonblock(1024)
+            rescue Errno::EAGAIN, IO::WaitReadable, EOFError
+              break
+            end while true
+          end
+        else
+          sleep 0.1
+        end
+        diff = tlimit - Time.now
       end
-      diff = tlimit - Time.now
-    end
-    if !waited
-      Process.kill(:KILL, pid)
-      Process.waitpid pid
-      faildesc = pretty(testsrc, "not finished in #{timeout_seconds} seconds", nil)
-    end
-    io.close
-    faildesc
-  }
+      if !waited
+        Process.kill(:KILL, pid)
+        Process.waitpid pid
+        faildesc = pretty(testsrc, "not finished in #{timeout_seconds} seconds", nil)
+      end
+      io.close
+      faildesc
+    }
+  end
 end
 
 def flunk(message = '')
-  newtest
-  show_progress('') { message }
+  add_assertion '', -> as do
+    as.show_progress('') { message }
+  end
+end
+
+def show_limit(testsrc, opt = '', **argh)
+  return if BT.quiet
+
+  add_assertion testsrc, -> as do
+    result = as.get_result_string(opt, **argh)
+    Assertion.errbuf << result
+  end
 end
 
 def pretty(src, desc, result)
@@ -460,66 +675,6 @@ def untabify(str)
   str.gsub(/^\t+/) {' ' * (8 * $&.size) }
 end
 
-def make_srcfile(src, frozen_string_literal: nil)
-  filename = 'bootstraptest.tmp.rb'
-  File.open(filename, 'w') {|f|
-    f.puts "#frozen_string_literal:true" if frozen_string_literal
-    f.puts "GC.stress = true" if $stress
-    f.puts "print(begin; #{src}; end)"
-  }
-  filename
-end
-
-def get_result_string(src, opt = '', **argh)
-  if @ruby
-    filename = make_srcfile(src, **argh)
-    begin
-      `#{@ruby} -W0 #{opt} #{filename}`
-    ensure
-      raise Interrupt if $? and $?.signaled? && $?.termsig == Signal.list["INT"]
-    end
-  else
-    eval(src).to_s
-  end
-end
-
-def with_stderr
-  out = err = nil
-  begin
-    r, w = IO.pipe
-    stderr = $stderr.dup
-    $stderr.reopen(w)
-    w.close
-    reader = Thread.start {r.read}
-    begin
-      out = yield
-    ensure
-      $stderr.reopen(stderr)
-      err = reader.value
-    end
-  ensure
-    w.close rescue nil
-    r.close rescue nil
-  end
-  return out, err
-end
-
-def newtest
-  @location = File.basename(caller(2).first)
-  @count += 1
-  cleanup_coredump
-end
-
-def error(msg, additional_message)
-  msg = "#{@failed}\##{@count} #{@location}#{@reset}: #{msg}  #{additional_message}"
-  if @tty
-    $stderr.puts "#{erase}#{msg}"
-  else
-    @errbuf.push msg
-  end
-  @error += 1
-end
-
 def in_temporary_working_directory(dir)
   if dir
     Dir.mkdir dir
@@ -547,21 +702,21 @@ def cleanup_coredump
     core_path = "/tmp/bootstraptest-core.#{Time.now.utc.iso8601}"
     warn "A core file is found. Saving it at: #{core_path.dump}"
     FileUtils.mv('core', core_path)
-    cmd = ['gdb', @ruby, '-c', core_path, '-ex', 'bt', '-batch']
+    cmd = ['gdb', BT.ruby, '-c', core_path, '-ex', 'bt', '-batch']
     p cmd # debugging why it's not working
     system(*cmd)
   end
   FileUtils.rm_f Dir.glob('core.*')
-  FileUtils.rm_f @ruby+'.stackdump' if @ruby
+  FileUtils.rm_f BT.ruby+'.stackdump' if BT.ruby
 end
 
 class CoreDumpError < StandardError; end
 
 def check_coredump
   if File.file?('core') or not Dir.glob('core.*').empty? or
-      (@ruby and File.exist?(@ruby+'.stackdump'))
+      (BT.ruby and File.exist?(BT.ruby+'.stackdump'))
     raise CoreDumpError, "core dumped"
   end
 end
 
-main
+exit main