Python

Python testing with unittest

• Show me the code
  • Implementation
  • Test
• Run this project using 🐳 docker
• Run this project locally

Show me the code

Implementation

1. Create HelloMessage class in hello_message.py:

class HelloMessage:
  def __init__(self):
    self.text = "Hello World!"

2. Create HelloConsole class in hello_console.py:

from builtins import print as __print__

class HelloConsole:
  def print(self, text):
    __print__(text)

Note that we have to import print system function as __print__ to avoid conflict with HelloConsole own print method.

3. Create HelloApp class in hello_app.py:

class HelloApp:
  def __init__(self, message, console):
    self.message = message
    self.console = console

  def print_hello(self):
    self.console.print(self.message.text)

4. Create main function in __main__.py that wraps it all together:

message = HelloMessage()
console = HelloConsole()
app = HelloApp(message, console)
app.print_hello()

Test

Following unittest > Basic example and unittest.mock > Quick Guide guides ...

1. Test HelloMessage in test_hello_message.py:

class HelloMessageTest(unittest.TestCase):
  def test_should_return_hello_world(self):
    message = HelloMessage()
    self.assertEqual(message.text, "Hello World!")

2. Test HelloApp in test_hello_app.py:

class HelloAppTest(unittest.TestCase):
  def test_should_print_hello_message(self):
    message_text = "Hello Test!"

    # 2.1 Create a mock of HelloMessage
    message = MagicMock()
    # 2.2 Return "Hello Test!" whenever text is called
    message.text = message_text

    # 2.3 Create a mock of HelloConsole
    console = MagicMock()
    # 2.4 Mock print method
    console.print = MagicMock()

    # 2.5 Create a HelloApp, the one we want to test, passing the mocks
    app = HelloApp(message, console)
    # 2.6 Execute the method we want to test
    app.print_hello()

    # 2.7 Verify HelloConsole mock print() method
    # has been called once with "Hello Test!"
    console.print.assert_called_once_with(message_text)

3. Test output should look like:

test_should_print_hello_message (test.test_hello_app.HelloAppTest.test_should_print_hello_message) ... ok
test_should_return_hello_world (test.test_hello_message.HelloMessageTest.test_should_return_hello_world) ... ok

----------------------------------------------------------------------
Ran 2 tests in 0.001s

OK

Run this project using 🐳 docker

• Execute ./docker-run.sh
• Once inside the container:
  • First time only, install dependencies with bundle install
  • Test with python -m unittest discover -v
  • Run with python -m main

Run this project locally

Pre-requisites

• Install Python manually or ...
  • Install pyenv version manager and ..
    • List available versions executing pyenv install -l
    • Install Python executing pyenv install 3.12 and pyenv global 3.12

Run locally

• Test with python -m unittest discover -v
• Run with python -m main

Create project from scratch

• As this project has no external modules required we do not need requirements.txt
• Just a bit of documentation on how to organize our code using packages