fix api pingpong peer address parse error handling and add test for it

pkg/api/pingpong.go

@@ -25,8 +25,9 @@ func (s *server) pingpongHandler(w http.ResponseWriter, r *http.Request) {
 
 	address, err := swarm.ParseHexAddress(peerID)
 	if err != nil {
-		s.Logger.Debugf("pingpong: ping %s: %v", peerID, err)
+		s.Logger.Debugf("pingpong: parse peer address %s: %v", peerID, err)
 		jsonhttp.BadRequest(w, "invalid peer address")
+		return
 	}
 
 	rtt, err := s.Pingpong.Ping(ctx, address, "hey", "there", ",", "how are", "you", "?")

pkg/api/pingpong_test.go

@@ -54,6 +54,13 @@ func TestPingpong(t *testing.T) {
 		})
 	})
 
+	t.Run("invalid peer address", func(t *testing.T) {
+		jsonhttptest.ResponseDirect(t, client, http.MethodPost, "/pingpong/invalid-address", nil, http.StatusBadRequest, jsonhttp.StatusResponse{
+			Code:    http.StatusBadRequest,
+			Message: "invalid peer address",
+		})
+	})
+
 	t.Run("error", func(t *testing.T) {
 		jsonhttptest.ResponseDirect(t, client, http.MethodPost, "/pingpong/"+errorPeerID.String(), nil, http.StatusInternalServerError, jsonhttp.StatusResponse{
 			Code:    http.StatusInternalServerError,