test.py

import cv2
import numpy as np
from app import color_to_bw

def test_color_to_bw():
    image = cv2.imread("test_image.jpg")
    expected_output = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    assert np.array_equal(color_to_bw(image), expected_output)

test_color_to_bw()