FakeFS::SpecHelpers provides a simple macro for RSpec example groups to turn FakeFS on and off. To use it simply require 'fakefs/spec_helpers', then include FakeFS::SpecHelpers into any example groups that you wish to use FakeFS in. For example:
require 'fakefs/spec_helpers' describe "Some specs that deal with files" do include FakeFS::SpecHelpers ... end
Alternatively, you can include FakeFS::SpecHelpers in all your example groups using RSpec’s configuration block in your spec helper:
require 'fakefs/spec_helpers' Spec::Runner.configure do |config| config.include FakeFS::SpecHelpers end
If you do the above then use_fakefs will be available in all of your example groups.