new_contents: import pytest
  import cv2
  import numpy as np
  from plantcv.plantcv.visualize import obj_sizes
  
  
  @pytest.mark.parametrize("num,expected", [[100, 4], [1, 4]])
  def test_obj_sizes(num, expected, test_data):
      img = cv2.imread(test_data.multi_bin_img, -1)
      visualization = obj_sizes(img=img, mask=img, num_objects=num)
      # Output unique colors are the 32 objects, the gray text, the black background, and white unlabeled leaves
      assert len(np.unique(visualization.reshape(-1, visualization.shape[2]), axis=0)) == expected
  
subject: Add obj_sizes tests module