def test_agent_controller_should_step_with_null_observation_cause_zero(mock_agent):
    """Test that AgentController's should_step method returns False for NullObservation with cause = 0."""
    # Create a mock event stream
    file_store = InMemoryFileStore()
    event_stream = EventStream(sid='test-session', file_store=file_store)

    # Create an agent controller
    controller = AgentController(
        agent=mock_agent,
        event_stream=event_stream,
        max_iterations=10,
        sid='test-session',
    )

    # Create a NullObservation with cause = 0
    # This should not happen, but if it does, the controller shouldn't step.
    null_observation = NullObservation(content='Test observation')
    null_observation._cause = 0  # type: ignore[attr-defined]

    # Check if should_step returns False for this observation
    result = controller.should_step(null_observation)

    # It should return False since we only want to step on NullObservation with cause > 0
    assert result is False, (
        'should_step should return False for NullObservation with cause = 0'
    )
Test that AgentController's should_step method returns False for NullObservation with cause = 0.
tests/unit/test_agent_controller.py