README.markdown

FakeFS

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.

Usage

    require 'fakefs'

    # That's it.

Don’t Fake the FS Immediately

    require 'fakefs/safe'

    FakeFS.activate!
    # your code
    FakeFS.deactivate!

    # or
    FakeFS do
      # your code
    end

RSpec

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.

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.

Caveats

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.

Speed?

<gist.github.com/156091>

Installation

### [Gemcutter](gemcutter.org/)

    $ gem install fakefs

### [Rip](hellorip.com)

    $ rip install git://github.com/defunkt/fakefs.git

Contributing

Once you’ve made your great commits:

[Fork][0] FakeFS
Create a topic branch - `git checkout -b my_branch`
Push to your branch - `git push origin my_branch`
Create an [Issue][1] with a link to your branch
That’s it!