nose2

nose2 Best Practices

nose2 is the modern successor to nose, built upon Python's unittest module. It offers powerful test discovery, a plugin architecture, and helpers for writing clean, maintainable test suites. This guide outlines essential best practices for leveraging nose2 effectively in your projects.

1. Project Layout & Naming

Always organize your tests in a dedicated tests/ directory at the root of your project. Name test files consistently using the test_*.py pattern. This ensures nose2's default discovery works reliably.

❌ BAD: Scattered tests or inconsistent naming

# Project root
my_module/
  feature_a.py
  feature_a_tests.py  # Inconsistent naming
  test_feature_b.py   # Mixed with source

✅ GOOD: Dedicated tests/ directory and test_*.py naming

# Project root
my_module/
  __init__.py
  feature_a.py
  feature_b.py
tests/
  __init__.py
  test_feature_a.py
  test_feature_b.py

2. Configuration (pyproject.toml)

Centralize all nose2 configuration within your pyproject.toml file under the [tool.nose2] table. This keeps your project configuration tidy, version-controlled, and compatible with modern Python tooling. Avoid unittest.cfg or nose2.cfg for new projects.

❌ BAD: Using legacy .cfg files

# unittest.cfg
[unittest]
start-dir = tests

✅ GOOD: pyproject.toml for all configuration

# pyproject.toml
[tool.nose2]
start-dir = "tests"
code-directories = ["src"] # Add your source code directories to sys.path if needed
plugins = [
    "nose2.plugins.coverage",
    "nose2.plugins.params",
    "nose2.plugins.junitxml",
]
exclude-plugins = [
    "nose2.plugins.loader.functions", # Avoid loading plain functions as tests
]

[tool.nose2.coverage]
always-on = true
coverage-combine = true # Essential for multiprocessing
coverage-report = ["term", "html"]
coverage-config = ".coveragerc"

3. Test Structure & Assertions

All tests must inherit from unittest.TestCase. Inside your test methods, use self.assert* methods provided by unittest.TestCase for detailed failure reports. Avoid raw assert statements, as they offer less diagnostic information on failure.