code: def test_normalized_diff_mask(b1_b2_arrs):
      """Test that if result does include nan values,
      the array is returned as masked."""
  
      # Test data
      b1, b2 = b1_b2_arrs
      b2 = b2.astype(float)
      b2[1:, 4:] = np.nan
  
      n_diff = es.normalized_diff(b1=b1, b2=b2)
  
      # Output array masked
      assert ma.is_masked(n_diff)
  
file_path: earthpy/earthpy/tests/test_norm_diff.py
imports: import numpy
  import numpy.ma
  import pytest
  import earthpy.spatial
label_desc: Use image node_id 5 for calling a global function with example usage: test_normalized_diff_mask(b1_b2_arrs) without return types