0417-pytest

Certainly! Here's a general, best-practice guide to using pytest—including directory structure, naming conventions, output control, and common pitfalls. This is suitable for teaching others or serving as a quick reference.

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✅ General Guide for Using pytest Effectively

📁 1. Recommended Project Structure

your_project/
├── src/                  # Optional, for better namespace control
│   └── your_package/
│       ├── __init__.py
│       ├── module1.py
│       └── module2.py
│
├── tests/                # All test files go here
│   ├── __init__.py       # Optional
│   ├── test_module1.py
│   └── test_module2.py
│
├── pyproject.toml        # Recommended modern config
├── requirements.txt
└── README.md

Alternatively, if you're not using src/ layout:

your_project/
├── your_package/
│   ├── __init__.py
│   ├── module1.py
│   └── ...
├── tests/
│   └── test_module1.py
└── ...

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🧪 2. Writing Tests

• Test files: name them as test_*.py or *_test.py

• Test functions: start names with test_

• Example:

# tests/test_module1.py
from your_package import module1

def test_add():
    assert module1.add(1, 2) == 3

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📦 3. Making Your Package Importable

From the root directory, run:

pip install -e .

This allows test files to import your package using absolute imports like:

from your_package import module1

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🖨️ 4. Seeing print() Output

By default, pytest captures stdout, so you won’t see print() unless:

• The test fails, or

• You run pytest with:

pytest -s            # disables output capturing
pytest --capture=no  # same effect

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⚠️ 5. Common Pitfalls to Avoid

Mistake	Why it's a problem
Placing test files in the same folder as code	Can cause import conflicts
Using relative imports in test files	Not robust; breaks easily
Naming a test file the same as a module	Import shadowing (test.py, math.py, etc.)
Forgetting to install in editable mode (-e .)	Causes ModuleNotFoundError in tests
Relying on print() without -s	Output won’t appear unless test fails

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⚙️ 6. Optional pyproject.toml Configuration

[tool.pytest.ini_options]
addopts = "-ra -q -s"
testpaths = ["tests"]
python_files = ["test_*.py"]

This simplifies your test command to just:

pytest

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Would you like a GitHub template or cookiecutter starter with this structure?