diff --git a/test/transaction.test.ts b/test/transaction.test.ts
index 6f335f5..ba31201 100644
--- a/test/transaction.test.ts
+++ b/test/transaction.test.ts
@@ -2,7 +2,7 @@ import * as ecc from 'tiny-secp256k1';
 import * as assert from 'assert';
 import { address, networks, Transaction } from 'liquidjs-lib';
 import { BlindingDataLike, Psbt } from 'liquidjs-lib/src/psbt';
-import { walletFromAddresses, WalletInterface } from '../src';
+import { Mnemonic, walletFromAddresses, WalletInterface } from '../src';
 import { greedyCoinSelector } from '../src/coinselection/greedy';
 import { fetchTxHex } from '../src/explorer/esplora';
 import { decodePset, psetToUnsignedHex, psetToUnsignedTx } from '../src/utils';
@@ -18,20 +18,20 @@ import secp256k1 from '@vulpemventures/secp256k1-zkp';
 jest.setTimeout(50000);
 
 let senderWallet: WalletInterface;
+let sender: Mnemonic;
 
 describe('buildTx', async () => {
   let USDT = '';
   let args: BuildTxArgs;
   let senderAddress = '';
   let senderBlindingKey = '';
-  const sender = await newRandomMnemonic();
 
   beforeAll(async () => {
     const zkplib = await secp256k1();
+    sender = await newRandomMnemonic();
     const addrI = await sender.getNextAddress();
     senderAddress = addrI.confidentialAddress;
     senderBlindingKey = addrI.blindingPrivateKey;
-
     senderWallet = await walletFromAddresses(
       ecc,
       zkplib,