如何在json.load()中使用mock_open?

问题描述

我正在尝试进行单元测试，该单元测试可以验证从JSON编码文件中读取凭证的功能.由于凭据本身不是固定的，因此单元测试需要提供一些凭据，然后测试它们是否已正确检索.

I'm trying to get a unit test working that validates a function that reads credentials from a JSON-encoded file. Since the credentials themselves aren't fixed, the unit test needs to provide some and then test that they are correctly retrieved.

这是凭证功能:

def read_credentials():
    basedir = os.path.dirname(__file__)
    with open(os.path.join(basedir, "authentication.json")) as f:
        data = json.load(f)
        return data["bot_name"], data["bot_password"]

这是测试:

def test_credentials(self):
    with patch("builtins.open", mock_open(
        read_data='{"bot_name": "name", "bot_password": "password"}\n'
    )):
        name, password = shared.read_credentials()
    self.assertEqual(name, "name")
    self.assertEqual(password, "password")

但是，当我运行测试时，json代码会因解码错误而崩溃.看一下json代码本身，我正在努力查看为什么模拟测试失败，因为json.load(f)只是调用f.read()然后再调用json.loads().

However, when I run the test, the json code blows up with a decode error. Looking at the json code itself, I'm struggling to see why the mock test is failing because json.load(f) simply calls f.read() then calls json.loads().

实际上，如果我将身份验证功能更改为以下内容，则单元测试有效:

Indeed, if I change my authentication function to the following, the unit test works:

def read_credentials():
    # Read the authentication file from the current directory and create a
    # HTTPBasicAuth object that can then be used for future calls.
    basedir = os.path.dirname(__file__)
    with open(os.path.join(basedir, "authentication.json")) as f:
        content = f.read()
        data = json.loads(content)
        return data["bot_name"], data["bot_password"]

我不必介意以这种形式保留我的代码，但是我想了解一下我的测试中是否有什么错误，可以使我的功能保持其原始形式.

I don't necessarily mind leaving my code in this form, but I'd like to understand if I've got something wrong in my test that would allow me to keep my function in its original form.

堆栈跟踪:

Traceback (most recent call last):
  File "test_shared.py", line 56, in test_credentials
shared.read_credentials()
  File "shared.py", line 60, in read_credentials
data = json.loads(content)
  File "/home/philip/.local/share/virtualenvs/atlassian-webhook-basic-3gOncDp4/lib/python3.6/site-packages/flask/json/__init__.py", line 205, in loads
return _json.loads(s, **kwargs)
  File "/usr/lib/python3.6/json/__init__.py", line 367, in loads
return cls(**kw).decode(s)
  File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.6/json/decoder.py", line 357, in raw_decode
raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

推荐答案

我遇到了同样的问题，并通过模拟json.load和builtins.open解决了这个问题:

I had the same issue and got around it by mocking json.load and builtins.open:

import json
from unittest.mock import patch, MagicMock

# I don't care about the actual open
p1 = patch( "builtins.open", MagicMock() )

m = MagicMock( side_effect = [ { "foo": "bar" } ] )
p2 = patch( "json.load", m )

with p1 as p_open:
    with p2 as p_json_load:
        f = open( "filename" )
        print( json.load( f ) ) 

结果:

{'foo': 'bar'}

这篇关于如何在json.load()中使用mock_open?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！