Mocha is great. But when your library is all about manipulating the filesystem, you really want to test the behavior and not the implementation.
If you're mocking and stubbing every call to FileUtils or File, you're tightly coupling your tests with the implementation.
def test_creates_directory FileUtils.expects(:mkdir).with("directory").once Library.add "directory" end
The above test will break if we decide to use mkdir_p
in our
code. Refactoring code shouldn't necessitate refactoring tests.
With FakeFS:
def test_creates_directory Library.add "directory" assert File.directory?("directory") end
Woot.
require 'fakefs' # That's it.
gem "fakefs", :require => "fakefs/safe" require 'fakefs/safe' FakeFS.activate! # your code FakeFS.deactivate! # or FakeFS do # your code end
If you are using fakefs in a rails project with bundler, you'll probably want to specify the following in your Gemfile:
gem “fakefs”, :require => “fakefs/safe”
The above approach works with RSpec as well. In addition you may include FakeFS::SpecHelpers to turn FakeFS on and off in a given example group:
require 'fakefs/spec_helpers' describe "my spec" do include FakeFS::SpecHelpers end
See lib/fakefs/spec_helpers.rb
for more info.
Third-party libraries may add methods to filesystem-related classes. FakeFS doesn't support these methods out of the
box, but you can define fake versions yourself on the equivalent FakeFS classes. For example, FileMagic adds
File#content_type
. A fake version can be provided as follows:
module FakeFS class File def content_type 'fake/file' end end end
FakeFS provides a test suite and works with symlinks. It's also strictly a test-time dependency: your actual library does not need to use or know about FakeFS.
FakeFS internally uses the Pathname
and FileUtils
constants. If you use these in your app, be
certain you're properly requiring them and not counting on FakeFS'
own require.
$ gem install fakefs
$ rip install git://github.com/defunkt/fakefs.git
Once you've made your great commits:
Create a topic branch - git checkout -b my_branch
Push to your branch - git push origin my_branch
Open a Pull Request
That's it!
Code: git clone git://github.com/defunkt/fakefs.git
Gems: rubygems.org/gems/fakefs
Update version in lib/fakefs/version.rb
Commit it
rake publish