Reviewboard 1.6.3 manage.py test run 0 test in 0.000s

Question

I am having a problem running test cases in reviewboard 1.6.3 The structure is goes like this

/reviewboard
  __init__.py
  settings.py
  settings_local.py
  manage.py
  /reviews
  __init__.py
  models.py
  tests.py

I have tried running: python manage.py test

but it keeps giving me

Ran 0 tests in 0.000s

Can someone tell me what am I doing wrong? I just want to run the tests.py

Code base is from this repository: https://github.com/reviewboard/reviewboard/tree/release-1.6.x