FSTest

Blatantly stolen file and directory assertion methods from Rails::Generators::TestCase. Include the FSTest module for testing file existence, and file contents.

gem install fstest

class MyClassTest < MiniTest::Unit::TestCase
  include FSTest

  def test_writes_file
    assert_no_file '/tmp/foo'
    File.open('/tmp/foo', 'w') {|fh| fh.puts "nom nom"}
    assert_file '/tmp/foo', /^nom nom$/
  end
end

I couldn't find any good examples of tests for Rails generators, so I looked at the Rails tests. Rails uses a custom test class called Rails::Generators::TestCase. This class has methods for testing the output of generators. I thought the methods would be useful outside of a Rails context, so I wrapped it up in the FSTest gem. Enjoy!

If you want to work with relative paths instead of absolute paths, you can set the 'base_directory' in a setup block.

class MyClassTest < MiniTest::Unit::TestCase
  include FSTest

  def setup
    # all assert_file assertions will be relative to your homedir
    self.base_directory = File.expand_path("~")
  end

  def test_dot_emacs
    # this will look for ~/.emacs
    assert_file '.emacs'
  end
end

I've also found it useful to use FakeFS alongside this.