require 'test_helper' class TestFile < Minitest::Test def setup File.open 'file', 'w' do |f| f.puts '1' f.puts '2' f.puts '3' end end def teardown FileUtils.rm 'file' if File.exist? 'copy' FileUtils.rm 'copy' end end def test_copylines File.copylines 'file', 'copy' do |line| "First line\n" if /1/ === line end assert_equal "First line\n2\n3\n", File.read('copy') end def test_copylines_on_the_same_file File.copylines 'file', 'file' do |line| "First line\n" if /1/ === line end assert_equal "First line\n2\n3\n", File.read('file') end end