setUp 跑了几次

（每道题开头都有同一段：被测模块 c_to_f / length，和一个静音跑测试的 run()，它交回「跑了几条/挂了几条/出错几条」。）

setUp 里给计数器加一，三条用例。运行程序，看它被调了几次：

import io, unittest

LEN = {"m": 1.0, "km": 1000.0, "cm": 0.01}

def c_to_f(c):
    return c * 9 / 5 + 32

def length(v, src, to):
    for u in (src, to):
        if u not in LEN:
            raise ValueError("不认识的单位：" + u)
    return v * LEN[src] / LEN[to]

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))

count = [0]

class T(unittest.TestCase):
    def setUp(self):
        count[0] += 1
        self.table = dict(LEN)
    def test_a(self):
        self.assertEqual(self.table["km"], 1000)
    def test_b(self):
        self.table["km"] = 1
        self.assertEqual(self.table["km"], 1)
    def test_c(self):
        self.assertEqual(self.table["km"], 1000)

print(run(T) + "/" + str(count[0]))