test1.jpg is used by running the following script, for example:

cd eRCaGuy_hello_world/python

./auto_white_balance_img.py 
# OR 
python3 auto_white_balance_img.py

This will generate two new files:

1. "eRCaGuy_hello_world/test_photos/test1_out1.jpg"
2. "eRCaGuy_hello_world/test_photos/test1_out2.jpg"

See my answer on Stack Overflow here for a demonstration and more details: How do I do the equivalent of Gimp's Colors, Auto, White Balance in Python-Fu?.