unit-test fix

Signed-off-by: Angelo De Caro <adc@zurich.ibm.com>

Author: adecaro

token/wallet_test.go

@@ -576,7 +576,7 @@ func TestOwnerWallet_Balance(t *testing.T) {
 	balance, err := wallet.Balance(ctx, WithType("USD"))
 
 	require.NoError(t, err)
-	assert.Equal(t, uint64(1000), balance)
+	assert.Equal(t, big.NewInt(1000), balance)
 }
 
 // TestOwnerWallet_RegisterRecipient verifies RegisterRecipient
@@ -768,7 +768,7 @@ func TestOwnerWallet_Balance_Error(t *testing.T) {
 
 	require.Error(t, err)
 	assert.Equal(t, expectedErr, err)
-	assert.Equal(t, uint64(0), balance)
+	assert.Nil(t, balance)
 }
 
 // TestIssuerWallet_ListIssuedTokens_Error verifies error handling