new_contents: import unittest
  from c2c.recipe.cssmin.buildout import relocate_urls
  
  class TestCssminRecipe(unittest.TestCase):
      def test_relocate_urls(self):
          # Same directory:
          self.assertEqual(relocate_urls("url( 'foo.png')", "/a/b/src.css", "/a/b/dest.css"), "url('foo.png')")
          # Same directory, relative path:
          self.assertEqual(relocate_urls("url( 'foo.png' )", "b/src.css", "b/dest.css"), "url('foo.png')")
          # Different directory:
          self.assertEqual(relocate_urls("url( 'foo.png' )", "/a/b/src.css", "/a/c/dest.css"), "url('../b/foo.png')")
          # Only handle url rules:
          self.assertEqual(relocate_urls("foo('foo.png' )", "/a/b/src.css", "/a/c/dest.css"), "foo('foo.png' )")
          
  
  if __name__ == '__main__':
      unittest.main()
  
subject: add unit tests for the relocate_urls function