为什么在单元测试期间无法读取环境变量？

Question

using vscode + pytest, while the test cases are written in unittest, for example:

class MyTest(unittest.TestCase):
    def testEnvVar(self):
        account = os.getenv("ACCOUNT")

It fails to read ACCOUNT . However, os.getenv("ACCOUNT") will get right result if it's executed by python test.py directly:

# test.py
import os
print(os.getenv("ACCOUNT"))

that ensure "ACCOUNT" envar is already set.

If executed by pytest tests/test.py , the envrionment var cannot be read too, so it's caused by pytest. I know pytest will do some tricks (for example, pytest will capture all console/stderr output), but I don't know what exactly it does to envar. And same as tox(in tox, you have to set passenv=* , so the test env can inherit all environment variables from shell where tox lives.

I mean, I totally understand this is trick that all test-related tools could make, I just don't know how to disable it in pytest. So don't suggest that I have forgot set variable, or my code is wrong, etc.

I know how to hack this, by use mock or add .env vars in vscode launch file. However, this will definitely expose account/password in some files/settings. since account and password are secrets, I don't want to expose them in any files.

I guess this is a very common requirement and pytest should have already hornored that. So why this still happend?

Answer 1

The easiest way is to use https://github.com/MobileDynasty/pytest-env . But I don't think you should test the enviroment variables in your unit tests.