public function testPayInvoice()
{
$this->client->post('invoiceitems', null, array('customer' => $this->customerId, 'amount' => 350, 'currency' => 'usd'));
$request = $this->invoices->createInvoiceRequest($this->customerId);
$invoice = $this->invoices->createInvoice($request);
$payResponse = $this->invoices->payInvoice($invoice->getId());
$this->assertInstanceOf(Invoices::INVOICE_RESPONSE_CLASS, $payResponse);
}