nose2: The Successor to nose, Based on unittest2

Introduction

nose2 is a robust testing framework for Python, serving as the official successor to the widely-used nose project. Built directly on Python's standard unittest module, nose2 extends its functionalities to offer a more flexible and feature-rich environment for writing and executing tests. Its primary goal is to simplify the testing process, making it more intuitive and powerful for Python developers. While pytest is a popular alternative for new projects, nose2 provides a strong, unittest-based solution, especially for those familiar with or migrating from nose.

Installation

Getting started with nose2 is straightforward. You can install it using pip:

pip install nose2

Examples

nose2 automatically discovers tests in Python files whose names start with test_ and runs every test function it finds.

Here's a basic example written in the standard unittest style:

# in test_simple.py
import unittest

class TestStrings(unittest.TestCase):
    def test_upper(self):
        self.assertEqual("spam".upper(), "SPAM")

You can run this test from your terminal:

$ nose2 -v
test_upper (test_simple.TestStrings) ... ok

----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

nose2 also provides additional tools and features beyond what unittest offers. For instance, you can use decorators like @params to run a test with multiple sets of arguments:

# in test_fancy.py
from nose2.tools import params

@params("Sir Bedevere", "Miss Islington", "Duck")
def test_is_knight(value):
    assert value.startswith('Sir')

Running this with nose2 -v --pretty-assert demonstrates its enhanced output:

$ nose2 -v --pretty-assert
test_fancy.test_is_knight:1
'Sir Bedevere' ... ok
test_fancy.test_is_knight:2
'Miss Islington' ... FAIL
test_fancy.test_is_knight:3
'Duck' ... FAIL

======================================================================
FAIL: test_fancy.test_is_knight:2
'Miss Islington'
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/mnt/ebs/home/sirosen/tmp/test_fancy.py", line 6, in test_is_knight
    assert value.startswith('Sir')
AssertionError

>>> assert value.startswith('Sir')

values:
    value = 'Miss Islington'
    value.startswith = <built-in method startswith of str object at 0x7f3c3172f430>
======================================================================
FAIL: test_fancy.test_is_knight:3
'Duck'
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/mnt/ebs/home/sirosen/tmp/test_fancy.py", line 6, in test_is_knight
    assert value.startswith('Sir')
AssertionError

>>> assert value.startswith('Sir')

values:
    value = 'Duck'
    value.startswith = <built-in method startswith of str object at 0x7f3c3172d490>
----------------------------------------------------------------------
Ran 3 tests in 0.001s

FAILED (failures=2)

Why Use nose2?

nose2 offers several compelling reasons for Python developers:

unittest Foundation: It builds upon the familiar unittest module, making it easy for developers already using unittest to transition and leverage nose2's enhancements.
Enhanced Test Discovery: Automatically finds and runs tests, reducing boilerplate configuration.
Extended Functionality: Provides powerful tools and plugins, such as parameterized tests (@params) and improved assertion output (--pretty-assert), which go beyond standard unittest capabilities.
Successor to nose: For projects migrating from the original nose framework, nose2 offers a modern and maintained alternative, though with some differences to be aware of.
Active Development: It supports current Python versions (Python 3) and aims to support PyPy and CPython betas.