pkg/gates: add unit test for String
pkg/gates: add unit test for String

Signed-off-by: Zhou Hao <f577ade201aa03d612c19915a089dc6084d45cd9@cn.fujitsu.com>

helm/helm,adamreese/helm,adamreese/deployment-manager,bacongobbler/helm,adamreese/deployment-manager,adamreese/deployment-manager,adamreese/helm,michelleN/deployment-manager,michelleN/deployment-manager,bacongobbler/helm,adamreese/deployment-manager,michelleN/deployment-manager,michelleN/deployment-manager,adamreese/deployment-manager,helm/helm