added test for is_valid_course
added test for is_valid_course

open-craft/edx-analytics-dashboard,open-craft/edx-analytics-dashboard,open-craft/edx-analytics-dashboard,rue89-tech/edx-analytics-dashboard,edx/edx-analytics-dashboard,Stanford-Online/edx-analytics-dashboard,nagyistoce/edx-analytics-dashboard,nagyistoce/edx-analytics-dashboard,rue89-tech/edx-analytics-dashboard,Stanford-Online/edx-analytics-dashboard,nagyistoce/edx-analytics-dashboard,edx/edx-analytics-dashboard,Stanford-Online/edx-analytics-dashboard,open-craft/edx-analytics-dashboard,rue89-tech/edx-analytics-dashboard,rue89-tech/edx-analytics-dashboard,edx/edx-analytics-dashboard,Stanford-Online/edx-analytics-dashboard,edx/edx-analytics-dashboard,nagyistoce/edx-analytics-dashboard