Test for EmptyCallOption

rpc_util_test.go

@@ -47,6 +47,8 @@ import (
 	"google.golang.org/grpc/transport"
 )
 
+var _ CallOption = EmptyCallOption{} // ensure EmptyCallOption implements the interface
+
 func TestSimpleParsing(t *testing.T) {
 	bigMsg := bytes.Repeat([]byte{'x'}, 1<<24)
 	for _, test := range []struct {