public function testCheckAmounts()
{
$invoice = new Invoice();
$item = new Item();
$item->setUnitaryCost(80);
$item->setQuantity(1);
$invoice->addItem($item);
// test amounts calculation
$invoice->checkAmounts();
$this->assertEquals(80, $invoice->getBaseAmount());
$this->assertEquals(80, $invoice->getNetAmount());
$this->assertEquals(0, $invoice->getTaxAmount());
$this->assertEquals(80, $invoice->getGrossAmount());
// Add the same item again.
$invoice->addItem($item);
$invoice->checkAmounts();
$this->assertEquals(0, $invoice->getTaxAmount());
$this->assertEquals(160, $invoice->getGrossAmount());
}