def use_fixture(name)
      path = File.join spec_root, 'fixtures', name.to_s
      copy_fixture path, active_fixture_dir
      Dir.chdir active_fixture_dir
      nil
    end
def use_fixture(name)
      path = File.join spec_root, 'fixtures', name.to_s
      copy_fixture path, active_fixture_dir
      Dir.chdir active_fixture_dir
      nil
    end
The next cog spec will execute in a fresh copy of the given fixture
 Fixture directories are stored in <tt>spec/fixtures</tt>.
 @param name [String] name of the fixture
 @return [nil]