Python - How To Write Pytest - Rico贾若童的博客

Run Pytest

Run a specific test file pytest path/to/test_file.py
Run a test in it: pytest path/to/test_file.py::test_function_name

Assert

For integer assertions:

assert (1==1)

For float assertions:

import pytest
1.0==pytest.approx(1.0)

For numpy array assertions:

import numpy as np
array1 = np.array([1, 2, 3])
array2 = np.array([1, 2, 3])
np.testing.assert_allclose(array1, array2)

Using VSCode Debugger With Pytest

ctrl+shift+p choose debug tests in the current file or debug all tests (if you want to debug all tests under a configured directory)
In my debugger, I found that I have to manually set a breakpoint before the failure point in Pytest. (I might miss an easier route to get around this)
At the failed test, right click, and choose debug test
pytest -s <my_test.py> seems to be executing all test modules in the current directory: this will be enforced in a pyproject.toml environment.

Test Fixture

The boiler plate is:

import pytest
@pytest.fixture
def basic_config():
    return {
        "batch_size": 2,
    }
def test_og_positional_encoder(basic_config):
    batch_size = basic_config["batch_size"]
    ...

Patching

Patching a Function

To patch my_func() from MyModule, pytest requires it to be a MagicMock object. This means we must specify return_value and pass mock_my_func into the test function.

from unittest.mock import patch
import requests

@patch('MyModule.my_func', return_value=my_func_patch())
def test_get_license_hash(mock_my_func):
    """Test if the server responds with 200 OK."""
    response = requests.get(f"{SERVER_URL}/GetLicenseHash")
    assert response.status_code == 200

Patching a Constant or List

Unlike functions, patching constants or lists does not require a MagicMock. Instead, patch directly replaces the original object with a real one, meaning no return_value or mock object argument is needed.

@patch('MyModule.WEBCAM_RESTART_COMMAND', ["echo", "hello"])
def test_webcam_restart():
    """Test if the webcam restart command is patched correctly."""
    response = requests.get(f"{SERVER_URL}/RestartService")
    assert response.status_code == 200

Python - How To Write Pytest

Pytest Is The New Black (Compared To Unittest)