fix: wait for the next lastId before sending a new transaction

web3.js/test/mockrpc/getlastid.js

@@ -0,0 +1,23 @@
+// @flow
+
+import {
+  Account,
+} from '../../src';
+import {url} from '../url';
+import {mockRpc} from '../__mocks__/node-fetch';
+
+export function mockGetLastId() {
+  const lastId = new Account();
+
+  mockRpc.push([
+    url,
+    {
+      method: 'getLastId',
+      params: [],
+    },
+    {
+      error: null,
+      result: lastId.publicKey.toBase58(),
+    }
+  ]);
+}