You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: test_add_user.rb
    path of file: ./repos/arvados/services/login-sync/test
    
    the code of the file until where you have to start completion: # Copyright (C) The Arvados Authors. All rights reserved.
#
# SPDX-License-Identifier: AGPL-3.0

require 'minitest/autorun'

require 'stubs'

class TestAddUser < Minitest::Test
  include Stubs

  def test_useradd_error
    valid_groups = %w(docker admin fuse).select { |g| Etc.getgrnam(g) rescue false }
    # binstub_new_user/useradd will exit non-zero because its args
    # won't match any line in this empty file:
    File.open(@tmpdir+'/succeed', 'w') do |f| end
    invoke_sync binstubs: ['new_user']
    spied = File.read(@tmpdir+'/spy')
    assert_match %r{useradd -m -c active -s /bin/bash active}, spied
    assert_match %r{useradd -m -c adminroot -s /bin/bash adminroot}, spied
  end

  def test_useradd_success
    # binstub_new_user/useradd will succeed.
    File.open(@tmpdir+'/succeed', 'w') do |f|
      f.puts 'useradd -m -c active
    
  def test_useradd_error
    valid_groups = %w(docker admin fuse).select { |g| Etc.getgrnam(g) rescue false }
    # binstub_new_user/useradd will exit non-zero because its args
    # won't match any line in this empty file:
    File.open(@tmpdir+'/succeed', 'w') do |f| end
    invoke_sync binstubs: ['new_user']
    spied = File.read(@tmpdir+'/spy')
    assert_match %r{useradd -m -c active -s /bin/bash active}, spied
    assert_match %r{useradd -m -c adminroot -s /bin/bash adminroot}, spied
  end

  def test_useradd_success
    # binstub_new_user/useradd will succeed.
    File.open(@tmpdir+'/succeed', 'w') do |f|
      f.puts 'useradd -m -c active -s /bin/bash -G active'
      f.puts 'useradd -m -c adminroot -s /bin/bash adminroot'
    end
    $stderr.puts "*** Expect crash after getpwnam() fails:"
    invoke_sync binstubs: ['new_user']
    assert !$?.success?
    spied = File.read(@tmpdir+'/spy')
    # Expect a crash after adding one user, because Dir.mkdir({home}) fails.
    assert_match %r{^useradd -m -c [^\n]+\n$}s, spied
  end
end