analytics: Add a few tests for fixtures.py.
analytics: Add a few tests for fixtures.py.

The code in fixtures.py is only called from populate_analytics_db, and is
only used for generating pretty fixture data for manual testing. This commit
adds tests for a few things that were easy to add tests for, and provides
some minimal coverage of the file, but is not meant to be comprehensive.

andersk/zulip,hackerkid/zulip,synicalsyntax/zulip,jackrzhang/zulip,jrowan/zulip,vabs22/zulip,christi3k/zulip,jrowan/zulip,tommyip/zulip,tommyip/zulip,brockwhittaker/zulip,Galexrt/zulip,vaidap/zulip,shubhamdhama/zulip,andersk/zulip,vabs22/zulip,mahim97/zulip,brockwhittaker/zulip,mahim97/zulip,dhcrzf/zulip,j831/zulip,timabbott/zulip,kou/zulip,shubhamdhama/zulip,shubhamdhama/zulip,brainwane/zulip,rishig/zulip,eeshangarg/zulip,Galexrt/zulip,Galexrt/zulip,verma-varsha/zulip,eeshangarg/zulip,zulip/zulip,jackrzhang/zulip,jphilipsen05/zulip,jackrzhang/zulip,synicalsyntax/zulip,andersk/zulip,vabs22/zulip,rishig/zulip,showell/zulip,jackrzhang/zulip,dhcrzf/zulip,verma-varsha/zulip,hackerkid/zulip,Galexrt/zulip,christi3k/zulip,dhcrzf/zulip,brainwane/zulip,eeshangarg/zulip,jrowan/zulip,punchagan/zulip,shubhamdhama/zulip,ryanbackman/zulip,rht/zulip,synicalsyntax/zulip,hackerkid/zulip,christi3k/zulip,hackerkid/zulip,brainwane/zulip,kou/zulip,timabbott/zulip,SmartPeople/zulip,christi3k/zulip,kou/zulip,rishig/zulip,timabbott/zulip,rishig/zulip,rht/zulip,eeshangarg/zulip,kou/zulip,tommyip/zulip,mahim97/zulip,hackerkid/zulip,shubhamdhama/zulip,hackerkid/zulip,vabs22/zulip,brockwhittaker/zulip,Galexrt/zulip,zulip/zulip,SmartPeople/zulip,brainwane/zulip,punchagan/zulip,SmartPeople/zulip,j831/zulip,vaidap/zulip,eeshangarg/zulip,punchagan/zulip,vaidap/zulip,verma-varsha/zulip,jackrzhang/zulip,jrowan/zulip,brockwhittaker/zulip,ryanbackman/zulip,rishig/zulip,andersk/zulip,zulip/zulip,jackrzhang/zulip,amanharitsh123/zulip,rishig/zulip,dhcrzf/zulip,jphilipsen05/zulip,brainwane/zulip,jphilipsen05/zulip,mahim97/zulip,eeshangarg/zulip,ryanbackman/zulip,zulip/zulip,punchagan/zulip,andersk/zulip,showell/zulip,punchagan/zulip,kou/zulip,showell/zulip,hackerkid/zulip,kou/zulip,christi3k/zulip,punchagan/zulip,jphilipsen05/zulip,Galexrt/zulip,mahim97/zulip,timabbott/zulip,jphilipsen05/zulip,mahim97/zulip,showell/zulip,rht/zulip,dhcrzf/zulip,jrowan/zulip,amanharitsh123/zulip,vaidap/zulip,amanharitsh123/zulip,kou/zulip,verma-varsha/zulip,timabbott/zulip,synicalsyntax/zulip,synicalsyntax/zulip,andersk/zulip,rht/zulip,SmartPeople/zulip,dhcrzf/zulip,vaidap/zulip,brockwhittaker/zulip,andersk/zulip,synicalsyntax/zulip,tommyip/zulip,jrowan/zulip,j831/zulip,SmartPeople/zulip,rht/zulip,tommyip/zulip,brainwane/zulip,SmartPeople/zulip,showell/zulip,punchagan/zulip,timabbott/zulip,rht/zulip,zulip/zulip,brainwane/zulip,brockwhittaker/zulip,jphilipsen05/zulip,j831/zulip,zulip/zulip,verma-varsha/zulip,shubhamdhama/zulip,amanharitsh123/zulip,amanharitsh123/zulip,christi3k/zulip,vaidap/zulip,rht/zulip,dhcrzf/zulip,Galexrt/zulip,ryanbackman/zulip,ryanbackman/zulip,j831/zulip,amanharitsh123/zulip,timabbott/zulip,synicalsyntax/zulip,showell/zulip,zulip/zulip,jackrzhang/zulip,tommyip/zulip,ryanbackman/zulip,tommyip/zulip,rishig/zulip,showell/zulip,vabs22/zulip,j831/zulip,eeshangarg/zulip,shubhamdhama/zulip,vabs22/zulip,verma-varsha/zulip