change fssourcetest to more declarative (#10458)
change fssourcetest to more declarative (#10458)

* add comments

* add comments

* add comments

smawson/istio,istio/istio,geeknoid/istio,geeknoid/istio,smawson/istio,smawson/istio,istio/istio,geeknoid/istio,smawson/istio,geeknoid/istio,smawson/istio,geeknoid/istio,istio/istio,smawson/istio,geeknoid/istio,istio/istio,istio/istio