def test_failed_sass_aborts(self, subprocess): fake_bin = self._make_fake_sass_bin() composer = SassComposer(fake_bin) source_file = '/in/sassy.scss' output_dir = '/out' subprocess.Popen.return_value.communicate.return_value = ('boom', '') subprocess.Popen.return_value.returncode = 1 with self.assertRaises(AbortError): composer.compose(None, source_file, output_dir)