function testCalculateCharge() { $item = new Item('Perfect PHP', 3600, '2010/11', 2); $this->assertIdentical($item->calculateCharge(1), 3600); $this->assertIdentical($item->calculateCharge(2), 7200); $item = new Item('Perfect PHP', 500, '2010/11', 2); $this->assertIdentical($item->calculateCharge(1), 500); $this->assertIdentical($item->calculateCharge(2), 1000); $this->assertFalse($item->calculateCharge(0)); $this->assertFalse($item->calculateCharge('string')); $this->assertFalse($item->calculateCharge(1.1)); $this->assertFalse($item->calculateCharge(null)); }