স্টেট ট্রানজিশন টেস্টিং

import unittest

ALLOWED = {
    "placed":    {"shipped", "cancelled"},
    "shipped":   {"delivered", "cancelled"},
    "delivered": set(),
    "cancelled": set(),
}

class Order:
    def __init__(self):
        self.state = "placed"

    def transition(self, new_state):
        if new_state not in ALLOWED[self.state]:
            raise ValueError(f"অবৈধ ট্রানজিশন: {self.state} -> {new_state}")
        self.state = new_state
        return self.state

# স্টেট মেশিনে সংজ্ঞায়িত সবগুলো বৈধ ট্রানজিশনের সেট -- কভারেজ যাচাইয়ের জন্য
ALL_VALID_TRANSITIONS = {(src, dst) for src, dests in ALLOWED.items() for dst in dests}

def do_transition(order, dest):
    src = order.state
    order.transition(dest)
    return (src, dest)

exercised = set()
o1 = Order()
exercised.add(do_transition(o1, "shipped"))
exercised.add(do_transition(o1, "delivered"))
o2 = Order()
exercised.add(do_transition(o2, "cancelled"))
o3 = Order()
exercised.add(do_transition(o3, "shipped"))
exercised.add(do_transition(o3, "cancelled"))

coverage_pct = len(exercised & ALL_VALID_TRANSITIONS) / len(ALL_VALID_TRANSITIONS) * 100
print(f"মোট বৈধ ট্রানজিশন: {len(ALL_VALID_TRANSITIONS)}")
print(f"টেস্ট সিকোয়েন্সে যাচাইকৃত ট্রানজিশন: {sorted(exercised)}")
print(f"স্টেট ট্রানজিশন কভারেজ: {coverage_pct:.0f}%")

class OrderStateTransitionTests(unittest.TestCase):
    def test_full_delivery_path(self):
        order = Order()
        self.assertEqual(order.transition("shipped"), "shipped")
        self.assertEqual(order.transition("delivered"), "delivered")

    def test_cancel_from_placed(self):
        order = Order()
        self.assertEqual(order.transition("cancelled"), "cancelled")

    def test_cancel_from_shipped(self):
        order = Order()
        order.transition("shipped")
        self.assertEqual(order.transition("cancelled"), "cancelled")

    def test_invalid_transition_rejected(self):
        order = Order()
        order.transition("shipped")
        order.transition("delivered")
        with self.assertRaises(ValueError):
            order.transition("shipped")  # delivered থেকে আর কোনো ট্রানজিশন বৈধ নয়

suite = unittest.TestLoader().loadTestsFromTestCase(OrderStateTransitionTests)
unittest.TextTestRunner(verbosity=2).run(suite)