tracing ut (#4320)
tracing ut (#4320)

* tracing ut

Signed-off-by: runzexia <root@junwuhui.cn>

* fix comments

Signed-off-by: RyderXia <ebdf197f9a397f12db3abd786a3a167c1185a426@sap.com>
knative/eventing,knative/eventing