Delete tests.py

app/tests.py

-# Python3 code to demonstrate
-# Add substring at specific index
-# using list slicing
-# initializing string
-test_string = 'GeeksGeeks'
-# initializing add_string
-add_string = "for"
-# printing original string
-print("The original string : " + test_string)
-add_string = 'italo'
-# printing add string
-print("The add string : " + add_string)
-