Organizing Code & Running unittest

Summary: in this tutorial, you’ll learn how to organize the test code and how to use the various commands to run unit tests.

Organizing code

If you have a few modules, you can create test modules and place them within the same directory.

In practice, you may have many modules organized into packages. Therefore, it’s important to keep the development code and test code more organized.

It’s a good practice to keep the development code and the test code in separate directories. And you should place the test code in a directory called test to make it obvious.

For demonstration purposes, we’ll create a sample project with the following structure:

D:\python-unit-testing
├── shapes
|  ├── circle.py
|  ├── shape.py
|  └── square.py
└── test
   ├── test_circle.py
   ├── test_square.py
   └── __init__.pyCode language: Python (python)

First, create the shapes and test directories in the project folder (python-unit-testing).

Second, create three modules shape.py, circle.py, and square.py modules and place them in the shapes directory.

shape.py

from abc import ABC, abstractmethod


class Shape(ABC):
    @abstractmethod
    def area() -> float:
        passCode language: Python (python)

The Shape class is an abstract class that has the area() method. It is the base class of the Circle and Square class.

circle.py

import math
from .shape import Shape


class Circle(Shape):
    def __init__(self, radius: float) -> None:
        if radius < 0:
            raise ValueError('The radius cannot be negative')

        self._radius = radius

    def area(self) -> float:
        return math.pi * math.pow(self._radius, 2)Code language: Python (python)

The Circle class also inherits from the Shape class. It implements the area() method that returns the area of the circle.

square.py

import math
from .shape import Shape


class Square(Shape):
    def __init__(self, length: float) -> None:
        if length < 0:
            raise ValueError('The length cannot be negative')
        self._length = length

    def area(self) -> float:
        return math.pow(self._length, 2)Code language: Python (python)

Like the Circle class, the Square class has the area() method that returns the area of the square.

Third, create the test_circle.py and test_square.py test modules and place them in the test folder:

test_circle.py

import unittest
import math

from shapes.circle import Circle
from shapes.shape import Shape


class TestCircle(unittest.TestCase):
    def test_circle_instance_of_shape(self):
        circle = Circle(10)
        self.assertIsInstance(circle, Shape)

    def test_create_circle_negative_radius(self):
        with self.assertRaises(ValueError):
            circle = Circle(-1)

    def test_area(self):
        circle = Circle(2.5)
        self.assertAlmostEqual(circle.area(), math.pi * 2.5*2.5)Code language: Python (python)

The test_circle module uses the Circle and Shape from the circle and shape test modules in the shapes package.

test_square.py

import unittest

from shapes.square import Square
from shapes.shape import Shape


class TestSquare(unittest.TestCase):

    def test_create_square_negative_length(self):
        with self.assertRaises(ValueError):
            square = Square(-1)

    def test_square_instance_of_shape(self):
        square = Square(10)
        self.assertIsInstance(square, Shape)

    def test_area(self):
        square = Square(10)
        area = square.area()
        self.assertEqual(area, 100)Code language: Python (python)

The test_square module uses the Square and Shape classes from the square and shape modules in the shapes package.

It’s important to create an __init__.py file and place it in the test folder. Otherwise, commands in the following section won’t work as expected.

Running unit tests

The unittest module provides you with many ways to run unit tests.

1) Running all tests

To run all tests in the test directory, you execute the following command from the project directory folder (python-unit-testing):

python -m unittest discover -vCode language: Python (python)

The discover is a subcommand that finds all the tests in the project.

Output:

test_area (test_circle.TestCircle) ... ok
test_circle_instance_of_shape (test_circle.TestCircle) ... ok
test_create_circle_negative_radius (test_circle.TestCircle) ... ok
test_area (test_square.TestSquare) ... ok
test_create_square_negative_length (test_square.TestSquare) ... ok
test_square_instance_of_shape (test_square.TestSquare) ... ok

----------------------------------------------------------------------
Ran 6 tests in 0.002s

OKCode language: Python (python)

2) Running a single test module

To run a single test module, you use the following command:

python -m unittest test_package.test_module -vCode language: Python (python)

For example, the following execute all tests in the test_circle module of the test package:

python -m unittest test.test_circle -vCode language: Python (python)

Output:

test_area (test.test_circle.TestCircle) ... ok
test_circle_instance_of_shape (test.test_circle.TestCircle) ... ok     
test_create_circle_negative_radius (test.test_circle.TestCircle) ... ok

---------------------------------------------------------------------- 
Ran 3 tests in 0.000s

OKCode language: Python (python)

3) Running a single test class

A test module may have multiple classes. To run a single test class in a test module, you use the following command:

python -m unittest test_package.test_module.TestClass -vCode language: Python (python)

For example, the following command tests the TestSquare class from the test_square module of the test package:

python -m unittest test.test_circle.TestCircle -vCode language: Python (python)

Output:

test_area (test.test_square.TestSquare) ... ok
test_create_square_negative_length (test.test_square.TestSquare) ... ok
test_square_instance_of_shape (test.test_square.TestSquare) ... ok

----------------------------------------------------------------------
Ran 3 tests in 0.001s

OKCode language: Python (python)

4) Running a single test method

To run a single test method of a test class, you use the following command:

python -m unittest test_package.test_module.TestClass.test_method -vCode language: Python (python)

For example, the following command tests the test_area() method of the TestCircle class:

python -m unittest test.test_circle.TestCircle.test_area -vCode language: Python (python)

Output:

test_area (test.test_circle.TestCircle) ... ok

----------------------------------------------------------------------
Ran 1 test in 0.001s

OKCode language: Python (python)

Summary

• Place the development code and test code in separate directories. It’s a good practice to store the test code in the test directory.
• Use the command python -m unittest discover -v to discover and execute all the tests.
• Use the command python -m unittest test_package.test_module -v to run a single test module.
• Use the command python -m unittest test_package.test_module.TestClass -v to run a single test class.
• Use the command python -m unittest test_package.test_module.TestClass.test_method -v to run a single test method.