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.
def test_creates_directory Library.add "directory" assert File.directory?("directory") end
require 'fakefs' # That's it.
Don't Fake the FS Immediately
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
lib/fakefs/spec_helpers.rb for more info.
Integrating with other filesystem libraries
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,
A fake version can be provided as follows:
module FakeFS class File def content_type 'fake/file' end end end
How is this different than MockFS?
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
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:
- Fork FakeFS
- 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!
git clone git://github.com/defunkt/fakefs.git
- Home: http://github.com/defunkt/fakefs
- Docs: http://defunkt.github.com/fakefs
- Bugs: http://github.com/defunkt/fakefs/issues
- List: http://groups.google.com/group/fakefs
- Test: http://travisci.org/#!/defunkt/fakefs
- Gems: http://rubygems.org/gems/fakefs
- Update version in lib/fakefs/version.rb
- Commit it
- rake publish