PyTest设置或销毁变量
PyTest设置或销毁变量
提问于 2018-05-31 18:47:00
如何为我的每个PyTests重新实例化一个变量？
具体地说，我希望每次创建一个新的StringIO()对象。
我当前的代码是：
output = StringIO()
def info_to_string(text):
output.write(text)
def write_to_file(some_text):
for row in some_text:
info_to_string(row)我需要在每次有新的测试夹具时设置output。
复制和粘贴代码以进行测试：
from io import StringIO
import pytest
output = StringIO()
def info_to_string(text):
output.write(text)
def write_to_file(some_text):
for row in some_text:
info_to_string(row)
def test_1():
write_to_file(['hello', 'there', 'what', 'is', 'up'])
print(output)
assert output.getvalue() == "hellotherewhatisup"
def test_2():
write_to_file(['nothing', 'much'])
assert output.getvalue() == "nothingmuch"
#This will error as the output is "hellotherewhatisupnothingmuch" if run after test_1因此，我需要为每个测试创建一个新的output = stringIO()。
回答 3
Stack Overflow用户
回答已采纳
发布于 2018-05-31 22:01:43
为了防止将来有人看到这一点，我的方法是创建一个类，重新初始化每个fixture
class WriteToString:
def __init__(self):
self.output = StringIO()
def info_to_string(self, text):
self.output.write(text)
@pytest.fixture
def write_to_string():
return WriteToString()并将测试更改为：
def test_2(write_to_string):
write_to_file(['nothing', 'much'])
assert write_to_string.output.getvalue() == "nothingmuch" Stack Overflow用户
发布于 2018-05-31 19:01:45
我不确定我是否完全理解了您的问题，但您可以像下面这样做，这将在您每次将其传递到测试函数时创建一个新的StringIO实例。如果你想每次都返回一个不同的字符串，我不认为你正在寻找一个fixture，而仅仅是一个泛型函数调用来帮你完成这项工作。
import pytest
from StringIO import StringIO
@pytest.fixture(scope='function')
def info_to_string():
output = StringIO()
output.write('blah')
return output
def test_something(info_to_string):
assert isinstance(info_to_string, StringIO)
assert info_to_string.getvalue() == 'blah'Stack Overflow用户
发布于 2018-05-31 21:20:10
我认为测试文件写入操作最简单的方法是使用tempfile。
但是，一旦提到StringIO作为测试策略的一部分，我的建议是将文件写入分为两部分。这为StringIO缓冲区提供了一个干净的入口点。
from pathlib import Path
from io import StringIO
import pytest
# Separate your data export to 2 functions, one operating
# with a filename, other with a file object.
def to_file(filename, content):
path = Path(filename)
if not path.exists():
path.touch()
with path.open('a') as f_obj:
write_to_file(f_obj, content)
# This is code under test. It must not be connected to your
# test code in any way, even if you have some version of "monkey-patching"
# in mind.
def write_to_file(file_object, content):
"""Dump *content* list of strings to *filename* with *writer*."""
for x in content:
file_object.write(str(x))
# This is test with StringIO buffer
def test_write_to_file_with_buffer():
buffer = StringIO()
# note you make several calls to write_to_file in one test, not across tests
# this helps keep tests isolated/independent
write_to_file(buffer, ['hello', 'there', 'what', 'is', 'up'])
write_to_file(buffer, ['nothing', 'much'])
assert buffer.getvalue() == 'hellotherewhatisupnothingmuch'页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/50622504
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