To make sure your tests are using a different broker than your orignal;
use these settings in your testing-settings.py:
CELERY_EAGER_PROPAGATES_EXCEPTIONS = True
CELERY_ALWAYS_EAGER = True
BROKER_BACKEND = 'memory'
For example, if your celery task updates the database, and you don't use these testing-settings, it will overwrite records in your "live" database instead of using the "test-database" what you are probably intending (!)