使用 Python unittest 缓存 setUp() 的结果 [英] Caching result of setUp() using Python unittest

问题描述

我目前有一个 unittest.TestCase 看起来像..

I currently have a unittest.TestCase that looks like..

class test_appletrailer(unittest.TestCase):
    def setup(self):
        self.all_trailers = Trailers(res = "720", verbose = True)

    def test_has_trailers(self):
        self.failUnless(len(self.all_trailers) > 1)

    # ..more tests..

这工作正常，但 Trailers() 调用需要大约 2 秒才能运行.鉴于 setUp() 在每个测试运行之前被调用，测试现在需要将近 10 秒才能运行(只有 3 个测试函数)

This works fine, but the Trailers() call takes about 2 seconds to run.. Given that setUp() is called before each test is run, the tests now take almost 10 seconds to run (with only 3 test functions)

在测试之间缓存 self.all_trailers 变量的正确方法是什么?

What is the correct way of caching the self.all_trailers variable between tests?

去掉setUp函数，然后做..

Removing the setUp function, and doing..

class test_appletrailer(unittest.TestCase):
    all_trailers = Trailers(res = "720", verbose = True)

..有效，但随后它声称在 0.000 秒内进行了 3 次测试"，这是不正确的.我能想到的唯一另一种方法是拥有一个 cache_trailers 全局变量(它工作正常，但相当可怕):

..works, but then it claims "Ran 3 tests in 0.000s" which is incorrect.. The only other way I could think of is to have a cache_trailers global variable (which works correctly, but is rather horrible):

cache_trailers = None
class test_appletrailer(unittest.TestCase):
    def setUp(self):
        global cache_trailers
        if cache_trailers is None:
            cache_trailers = self.all_trailers = all_trailers = Trailers(res = "720", verbose = True)
        else:
            self.all_trailers = cache_trailers

推荐答案

如何使用只初始化一次的类成员?

How about using a class member that only gets initialized once?

class test_appletrailer(unittest.TestCase):

    all_trailers = None

    def setup(self):
        # Only initialize all_trailers once.
        if self.all_trailers is None:
            self.__class__.all_trailers = Trailers(res = "720", verbose = True)

引用 self.all_trailers 的查找将进入 MRO -- self.__class__.all_trailers，将被初始化.

Lookups that refer to self.all_trailers will go to the next step in the MRO -- self.__class__.all_trailers, which will be initialized.

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