diff --git a/tests/test_main.py b/tests/test_main.py
index 9050603..554c51d 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -51,6 +51,36 @@ def test_5(self):
         order_1 = c.Order(id="1", items=[service])
         self.assertEqual(c.validorder(order_1), "Invalid item type: service")
 
+    # Tricks the system and walks away with 1 television, despite valid payment & reimbursement
+    def test_6(self):
+        tv_item = c.Item(type='product', description='tv', amount=1000.00, quantity=1)
+        payment = c.Item(type='payment', description='invoice_4', amount=1e19, quantity=1)
+        payback = c.Item(type='payment', description='payback_4', amount=-1e19, quantity=1)
+        order_4 = c.Order(id='4', items=[payment, tv_item, payback])
+        self.assertEqual(c.validorder(order_4), 'Order ID: 4 - Payment imbalance: $-1000.00')
+
+    # Valid payments that should add up correctly, but do not
+    def test_7(self):
+        small_item = c.Item(type='product', description='accessory', amount=3.3, quantity=1)
+        payment_1 = c.Item(type='payment', description='invoice_5_1', amount=1.1, quantity=1)
+        payment_2 = c.Item(type='payment', description='invoice_5_2', amount=2.2, quantity=1)
+        order_5 = c.Order(id='5', items=[small_item, payment_1, payment_2])
+        self.assertEqual(c.validorder(order_5), 'Order ID: 5 - Full payment received!')
+
+    # The total amount payable in an order should be limited
+    def test_8(self):
+        num_items = 12
+        items = [c.Item(type='product', description='tv', amount=99999, quantity=num_items)]
+        for i in range(num_items):
+            items.append(c.Item(type='payment', description='invoice_' + str(i), amount=99999, quantity=1))
+        order_1 = c.Order(id='1', items=items)
+        self.assertEqual(c.validorder(order_1), 'Total amount payable for an order exceeded')
+
+        # Put payments before products
+        items = items[1:] + [items[0]]
+        order_2 = c.Order(id='2', items=items)
+        self.assertEqual(c.validorder(order_2), 'Total amount payable for an order exceeded')
+
 
 if __name__ == "__main__":
     unittest.main()