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How to Set Environment Variable In Pytest?

2 minutes read

To set an environment variable in pytest, you can use the --env flag followed by the name of the variable and its value. For example, to set the ENVIRONMENT variable to production you can run pytest --env ENVIRONMENT=production. This allows you to customize the environment variables used during testing without modifying your code. Environment variables can also be set using the os module in Python within your test code or via a pytest fixture. Setting environment variables in pytest is useful for configuring different testing scenarios and ensuring your tests run consistently across different environments.


What is the syntax for setting environment variables in pytest?

In pytest, environment variables can be set using the os module in Python. Here is an example of setting an environment variable in pytest:

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import os
import pytest

@pytest.fixture(autouse=True)
def set_env_variable():
    os.environ['MY_ENV_VAR'] = 'my_value'

def test_example():
    assert os.environ.get('MY_ENV_VAR') == 'my_value'


In this example, the set_env_variable fixture sets the environment variable MY_ENV_VAR to the value my_value before each test function is executed. The test_example function then checks if the environment variable is set correctly.


What is the purpose of setting environment variables in pytest?

Setting environment variables in pytest allows you to customize the testing environment and configure certain behaviors or settings that are necessary for your tests to run properly. For example, you can set environment variables to specify a different database connection, set specific configurations, define paths to files or directories, or pass other settings that your tests may rely on. This helps to ensure that your tests are run consistently and reliably across different environments.


How to mock environment variables for unit testing in pytest?

To mock environment variables for unit testing in pytest, you can use the monkeypatch fixture provided by pytest. Here's an example of how you can mock environment variables in a unit test:

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# my_module.py
import os

def get_secret_key():
    return os.environ.get('SECRET_KEY')

# test_my_module.py
import os
import pytest
from my_module import get_secret_key

def test_get_secret_key(monkeypatch):
    # Mock the environment variable
    monkeypatch.setenv('SECRET_KEY', 'mocked_secret_key')

    # Call the function that uses the environment variable
    secret_key = get_secret_key()

    assert secret_key == 'mocked_secret_key'


In this example, we are using the monkeypatch fixture provided by pytest to mock the SECRET_KEY environment variable. We set the value of the environment variable to 'mocked_secret_key' using monkeypatch.setenv(). Then, we call the get_secret_key() function from my_module and assert that it returns the mocked value.


By using the monkeypatch fixture in this way, we can easily mock environment variables for unit testing in pytest.

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