stream_events: Add tests for mark_subscribed.
stream_events: Add tests for mark_subscribed.

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