Remove an enumerate call

Refactor tests/test_backend.py, remove a useless enumerate call in
for loop.

Change-Id: I5d1914ae3490f715437711d594ec903a2c6632f5
Correct Spelling Mistake

Modified one spelling mistake in tests/test_middleware

Change-Id: I4beffa77c38321a44b44d1893d2335319c23b5a5
Merge "Remove an enumerate call"
Merge "Correct Spelling Mistake"