"""
Example for running pytest.
"""

import pytest

class Simulation:
   
    def __init__(self):
        """
        Initializer for a simulation object.
        """
        self._distortions = []  # list of lists containing distortion vectors

    def get_distortion_vector(self, idx):
        if idx >= len(self._distortions) or idx < 0:
            raise IndexError("Invalid distortion vector index.")
        return self._distortions[idx]

    def register_distortion_vector(self, distortion):
        """
        Append a distortion vector to the simulation's distortion register.
        
        Parameter:
        distortion: List (3D) to be added to the distortion register.
        """
        if len(distortion) != 3:
            raise ValueError("Invalid distortion vector dimension.")
        self._distortions.append(distortion)

@pytest.fixture
def test_first_distortion():
    return [1.001, 0.998, 1.001]

@pytest.fixture
def test_second_distortion():
    return [0.999, 1.002, 0.999]

@pytest.fixture
def test_sim_object(test_first_distortion, test_second_distortion):
    s = Simulation()
    s.register_distortion_vector(test_first_distortion)
    s.register_distortion_vector(test_second_distortion)
    return s

def test_vector_order(test_first_distortion, test_second_distortion, test_sim_object):
    v = test_sim_object.get_distortion_vector(0)
    for d in range(3):
        assert v[d] == pytest.approx(test_first_distortion[d])
        
    v = test_sim_object.get_distortion_vector(1)
    for d in range(3):
        assert v[d] == pytest.approx(test_second_distortion[d])
    
    with pytest.raises(IndexError) as excinfo:
        v = test_sim_object.get_distortion_vector(2)
    assert str(excinfo.value) == "Invalid distortion vector index."