itest: Checking the total num of payments

When there are no payments expected returning, besides
checking if the paymensts is empty, check also if the
total num of payments is zero

itest/lnd_payment_test.go

@@ -256,6 +256,14 @@ func testListPayments(ht *lntest.HarnessTest) {
 				endDate:  createTimeSeconds - 1,
 				expected: false,
 			},
+			{
+				// Use an earlier both start date and end date 
+				// should return us nothing.
+				name:     "earlier start and end date",
+				startDate: createTimeSeconds - 2,
+				endDate:  createTimeSeconds - 1,
+				expected: false,
+			},
 		}
 	}
 
@@ -273,13 +281,19 @@ func testListPayments(ht *lntest.HarnessTest) {
 			req := &lnrpc.ListPaymentsRequest{
 				CreationDateStart: tc.startDate,
 				CreationDateEnd:   tc.endDate,
+				CountTotalPayments: true,
 			}
 			resp := alice.RPC.ListPayments(req)
 
 			if tc.expected {
 				require.Lenf(t, resp.Payments, 1, "req=%v", req)
+				require.Equal(t, resp.TotalNumPayments,
+					uint64(1),
+					"TNP=%v", resp.TotalNumPayments)
 			} else {
 				require.Emptyf(t, resp.Payments, "req=%v", req)
+				require.Zero(t, resp.TotalNumPayments,
+					"TNP=%v", resp.TotalNumPayments)
 			}
 		})
 	}