What is the difference between Pytest and Unittest in Python?

1. Installation and use

In terms of installation, Unittest is definitely better because there is no need to install it. Unittest belongs to the Python standard library and is installed when Python is installed. The installation of Pytest only needs to be installed through pip, which is not complicated. The above is the installation, but what about use?

Pytest is more flexible in use. You can use various options on the command line to execute tests, while Unittest requires writing test cases in scripts and using the Unittest module to run tests. Pytest gets more points at this point.

2. Writing test cases

There are also some differences between Pytest and Unittest in writing test cases. Compared with Unittest, Pytest's test case writing is more concise. Pytest uses Python's assert keyword to assert test results, while Unittest needs to use assertEqual, assertTrue and other methods to assert.

The following is an example of a test case written using Pytest. The purpose of the test case is to test the following class:

class Calculator:  
    def add(self, a, b):  
        return a + b  
  
    def subtract(self, a, b):  
        return a - b

If written in Pytest

import pytest  
  
from Calc import Calculator  
  
  
@pytest.mark.parametrize("a, b, expected", [  
    (2, 3, 5),  
    (0, 0, 0),  
    (-1, 1, 0),  
])  
def test_calculator_add(a, b, expected):  
    calculator = Calculator()  
    assert calculator.add(a, b) == expected

but written using Unittest The same test case is:

import unittest  
  
from Calc import Calculator  
  
  
class TestCalculator(unittest.TestCase):  
    def test_calculator_add(self):  
        calculator = Calculator()  
        self.assertEqual(calculator.add(2, 3), 5)  
        self.assertEqual(calculator.add(0, 0), 0)  
        self.assertEqual(calculator.add(-1, 1), 0)

Unittest must create a test class, so in most scenarios, Pytest will get more points when discussing code simplicity. And we can compare the output:

The following is the output result of Pytest

====================== ======= test session starts =============================
collecting ... collected 3 items

test_calc.py::test_calculator_add[2-3-5] PASSED [ 33%]
test_calc.py::test_calculator_add[0-0-0] PASSED [ 66%]
test_calc .py ::test_calculator_add[-1-1-0] PASSED [100%]
##============================ == 3 passed in 0.01s ==============================

The following is the Unittest Output result

============================= test session starts ======= ======================

collecting ... collected 1 item

u.py::TestCalculator::test_calculator_add PASSED %]

============================== 1 passed in 0.01s ======= =======================

Comparison found that pytest will output detailed results, while unittest gives overall results judge. Therefore, Pytest is superior in terms of friendliness.

3. Automatically discover test cases

Pytest can automatically discover test cases, which means that we do not need to manually write code to identify which test cases should be executed. Unittest requires manually specifying the execution order and execution method of test cases in the script.

4. Plug-ins and extensions

Pytest has a rich set of plug-ins and extensions that can be used to enhance the functionality of the testing framework. Unittest is relatively simple and does not have as many extensions as Pytest.

5. Running speed

In terms of running speed, Pytest is faster than Unittest. This is because Pytest can execute test cases in parallel, while Unittest can only execute test cases in sequence.

6. Report

Both Pytest and Unittest can generate test reports, but Pytest’s test report is more friendly and easy to read. Pytest's test report contains test case execution results, time, failure information, etc., while Unittest's test report is relatively simple.

7. Community Support

Pytest has a huge community support, so you can easily find relevant documentation and solutions when using Pytest. In comparison, Unittest's community support is relatively small.

In general, Pytest is more flexible, simpler, and has more extensions than Unittest. If you want to write test cases quickly and need more extended functionality, then Pytest will be a better choice. But if you need more control and refined testing, Unittest may be more suitable for you.

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