workaround to avoid suspending rb-readline by 'Ctrl-Y'. https://arika.org/2017/11/10/rb-readline-and-ctrl-y/

.irbrc

# macOSでのrb-readline使用時の"\C-y"サスペンド問題の回避
if defined?(::RbReadline) && $".grep(/\/rbreadline.rb\z/)
  stty = `stty -a`
  stty_ccs = { 'dsusp' => '^Y', 'lnext' => '^V' }
  stty_ccs.delete_if {|cc, key| /\b#{Regexp.quote("#{cc} = #{key}")};/ !~ stty }

  unless stty_ccs.empty?
    system('stty', *stty_ccs.keys.inject([]) {|opts, cc| opts << cc << 'undef' })

    IRB.conf[:AT_EXIT] << proc do
      system('stty', *stty_ccs.to_a.flatten)
    end
  end
end

.pryrc

# macOSでのrb-readline使用時の"\C-y"サスペンド問題の回避
stty_ccs = {}
nest_level = -1

Pry.hooks.add_hook(:when_started, 'avoid dsusp') do
  if defined?(::RbReadline) && $".grep(/\/rbreadline.rb\z/)
    stty = `stty -a`
    stty_ccs = { 'dsusp' => '^Y', 'lnext' => '^V' }
    stty_ccs.delete_if {|cc, key| /\b#{Regexp.quote("#{cc} = #{key}")};/ !~ stty }
  end
end

Pry.hooks.add_hook(:before_session, 'count nest level') do
  nest_level += 1
end

Pry.hooks.add_hook(:before_session, 'avoid dsusp') do |_, _, pry|
  system('stty', *stty_ccs.keys.inject([]) {|opts, cc| opts << cc << 'undef' }) if nest_level.zero? && !stty_ccs.empty?
end

Pry.hooks.add_hook(:after_session, 'avoid dsusp') do |_, _, pry|
  system('stty', *stty_ccs.to_a.flatten) if nest_level.zero? && !stty_ccs.empty?
end

Pry.hooks.add_hook(:after_session, 'count nest level') do
  nest_level -= 1
end

test.rb

require 'pty'
require 'timeout'

irb_start = [
  'gem "rb-readline"', # rb-readlineを使用しない場合はコメントアウト
  'require "irb"',
  'IRB.start',
].join('; ')

timeout = 5
bash_prompt = /bash-[.\d]+\$ \z/
irb_prompt = />> \z/

ios = [
  bash_prompt,
  "echo cat test\n",
  bash_prompt,
  "cat\n",
  "aaa\n",
  "bbb\n",
  "\C-d",
  bash_prompt,
  "echo readline test\n",
  bash_prompt,
  "ruby -e '#{irb_start}' -- -f --prompt-mode=simple\n",
  irb_prompt,
  ":ccc\n",
  irb_prompt,
  ":ddd", "\C-a", "\C-k", "eee = ", "\C-y", "\n",
  irb_prompt,
  ":fff\n",
  irb_prompt,
  "quit\n",
  bash_prompt,
  "echo done.\n",
  bash_prompt,
  "exit\n",
]

result = 'OK'
wait = nil
buf = ''

PTY.spawn('bash --norc') do |r, w, _p|
  w.sync = true

  begin
    Timeout.timeout(timeout) do
      ios.each do |obj|
        if obj.is_a?(String)
          w.write obj
          $stderr.write '+'
          next
        end

        wait = obj
        loop do
          buf << r.readpartial(1024)
          break if wait.match(buf)
          $stderr.write '-'
          sleep 0.1
        end
        $stderr.write '.'
      end
    end

    buf << r.readpartial(1024)
  rescue Timeout::Error
    result = "ERROR: couldn't get #{wait.inspect}"
  ensure
    w.close
    r.close
  end
end

$stderr.write "\n#{'-' * 78}\n"
print "RESULT = #{result}\n\n#{buf}"

test.rb-output-with-rb-readline.txt

$ ruby test.rb
-.+-.++++-.+-.+--.+-.++++++---
------------------------------------------------------------------------------
RESULT = ERROR: couldn't get />> \z/

bash-3.2$ echo cat test
cat test
bash-3.2$ cat
aaa
bbb
aaa
bbb
bash-3.2$ echo readline test
readline test
ode=simpleruby -e 'gem "rb-readline"; require "irb"; IRB.start' -- -f --prompt-m
>> :ccc
=> :ccc
>> eee =
[1]+  Stopped                 ruby -e 'gem "rb-readline"; require "irb"; IRB.start' -- -f --prompt-mode=simple
bash-3.2$

test.rb-output-without-rb-readline.txt

$ ruby test.rb
.+-.++++-.+-.+--.+--.++++++---.+--.+-.+-.+
------------------------------------------------------------------------------
RESULT = OK

bash-3.2$ echo cat test
cat test
bash-3.2$ cat
aaa
bbb
aaa
bbb
bash-3.2$ echo readline test
readline test
bash-3.2$ ruby -e 'require "irb"; IRB.start' -- -f --prompt-mode=simple
>> :ccc
=> :ccc
>> eee = :ddd
=> :ddd
>> :fff
=> :fff
>> quit
bash-3.2$ echo done.
done.