with_fakefs

>> $LOAD_PATH << "."
=> ["/Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/lib/ruby/gems/2.6.0/gems/did_you_mean-1.3.0/lib", "/Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/lib/ruby/site_ruby/2.6.0", "/Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/lib/ruby/site_ruby/2.6.0/x86_64-darwin20", "/Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/lib/ruby/site_ruby", "/Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/lib/ruby/vendor_ruby/2.6.0", "/Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/lib/ruby/vendor_ruby/2.6.0/x86_64-darwin20", "/Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/lib/ruby/vendor_ruby", "/Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/lib/ruby/2.6.0", "/Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/lib/ruby/2.6.0/x86_64-darwin20", "."]
>> require 'fakefs'
=> true
>> File.touch("foo")
Traceback (most recent call last):
        4: from /Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/bin/irb:23:in `<main>'
        3: from /Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/bin/irb:23:in `load'
        2: from /Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/lib/ruby/gems/2.6.0/gems/irb-1.0.0/exe/irb:11:in `<top (required)>'
        1: from (irb):6
NoMethodError (undefined method `touch' for FakeFS::File:Class)
>> FileUtils.touch("foo")
=> ["foo"]
>> IO.read("foo")
Traceback (most recent call last):
        5: from /Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/bin/irb:23:in `<main>'
        4: from /Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/bin/irb:23:in `load'
        3: from /Users/smtlaissezfaire/.rvm/rubies/ruby-2.6.6/lib/ruby/gems/2.6.0/gems/irb-1.0.0/exe/irb:11:in `<top (required)>'
        2: from (irb):8
        1: from (irb):8:in `read'
Errno::ENOENT (No such file or directory @ rb_sysopen - foo)

with_native_ruby

/Users/smtlaissezfaire/src/fakefs/lib (master)$ irb
>> FileUtils
=> FileUtils
>> FileUtils.touch("foo")
=> ["foo"]
>> IO.read("foo")
=> ""