text: 
  from singularity_stack import ConstraintEvaluator
  import socket
  import pytest
  
  def test_eval():
      ce = ConstraintEvaluator()
      assert ce('foo-1') == 'foo-1'
      assert ce('node.hostname == {}'.format(socket.gethostname().split('.')[0]))
      assert not ce('node.hostname == {}-notaname'.format(socket.gethostname().split('.')[0]))
      
      with pytest.raises(ValueError):
          ce('node.hostname > 1')
      with pytest.raises(ValueError):
          ce('node.label.foo == blah')
  