共用一个会怎样

（每道题开头都有同一段：上面那套被测系统、unittest 和 mock，以及 eng_07 的静音 run(*cases)——交回「跑了几条/挂了几条/出错几条」。）

把 Store 建成类属性，三条测试共用。再数每条看到几样：

import io, unittest
from unittest import mock

def parse(line):
    w = line.split()
    if len(w) != 3:
        raise ValueError("格式不对：" + line)
    return w[0], int(w[1]), float(w[2])


def subtotal(qty, price):
    return qty * price


def discount(amount):
    return amount * 0.9 if amount >= 100 else amount


class Store:
    def __init__(self):
        self.items = []

    def add(self, name, qty, price):
        self.items.append((name, qty, price))

    def total(self):
        return discount(sum(subtotal(q, p) for _, q, p in self.items))


def fmt(x):
    return ("%.2f" % x).rstrip("0").rstrip(".")


def report(store, rate):
    lines = [n + " " + str(q) + " " + fmt(subtotal(q, p)) for n, q, p in store.items]
    t = store.total()
    lines.append("合计 " + fmt(t) + " 约 " + fmt(t / rate) + " 外币")
    return "\n".join(lines)


def fetch_rate():
    raise ConnectionError("没有网络：汇率服务连不上")


def handle(lines, get_rate=fetch_rate):
    store = Store()
    for line in lines:
        n, q, p = parse(line)
        store.add(n, q, p)
    return report(store, get_rate())


def run(*cases):
    suite = unittest.TestSuite()
    for c in cases:
        suite.addTests(unittest.defaultTestLoader.loadTestsFromTestCase(c))
    r = unittest.TextTestRunner(stream=io.StringIO()).run(suite)
    return str(r.testsRun) + "/" + str(len(r.failures)) + "/" + str(len(r.errors))


SEEN = []

class TestShared(unittest.TestCase):
    store = Store()

    def test_a(self):
        self.store.add("西瓜", 2, 30)
        SEEN.append(len(self.store.items))

    def test_b(self):
        SEEN.append(len(self.store.items))
        self.assertEqual(len(self.store.items), 0)

    def test_c(self):
        self.store.add("米", 10, 4.2)
        SEEN.append(len(self.store.items))

print(run(TestShared) + "/" + ",".join(str(x) for x in SEEN))