    @Test
    public void testGenerateCentralWalletHash() throws BlockchainException {

        when(this.transactionService.getByReceiverHash(anyString())).thenReturn(null);
        when(this.walletService.create(any(Wallet.class))).thenAnswer(new Answer<Wallet>() {
            @Override
            public Wallet answer(final InvocationOnMock invocation) throws Throwable {
                final Wallet wallet = invocation.getArgumentAt(0, Wallet.class);
                FileUtils.write(new File("src/test/resources/content1.cnt"), wallet.getContent());
                return wallet;
            }

        });
        final String hash1 = this.service.generateCentralWalletHash();
        final String hash2 = this.service.generateCentralWalletHash();
        Assert.assertFalse(hash1.equals(hash2));
    }