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A unit test class that validates the functionality of the EmailHandler class, specifically testing email forwarding success and failure scenarios using mocked O365Client dependencies.

Purpose

This test class ensures the EmailHandler's forward_email method works correctly by testing both successful email forwarding and error handling when email sending fails. It uses unittest.mock to patch the O365Client.send_email method, allowing isolated testing without actual email transmission. The tests verify that the EmailHandler correctly processes incoming email dictionaries and calls the O365Client with appropriate parameters.

Source Code

class TestEmailHandler(TestCase):

    @patch.object(O365Client, 'send_email')
    def test_forward_email_success(self, mock_send_email):
        # Arrange
        email_handler = EmailHandler()
        mock_send_email.return_value = True
        incoming_email = {
            'from': 'test@example.com',
            'to': 'forwarded@example.com',
            'subject': 'Test Subject',
            'body': 'This is a test email.'
        }

        # Act
        result = email_handler.forward_email(incoming_email)

        # Assert
        self.assertTrue(result)
        mock_send_email.assert_called_once_with(
            to_addresses=['forwarded@example.com'],
            subject='Test Subject',
            body_html='This is a test email.',
            body_text='This is a test email.'
        )

    @patch.object(O365Client, 'send_email')
    def test_forward_email_failure(self, mock_send_email):
        # Arrange
        email_handler = EmailHandler()
        mock_send_email.side_effect = Exception("Email sending failed")
        incoming_email = {
            'from': 'test@example.com',
            'to': 'forwarded@example.com',
            'subject': 'Test Subject',
            'body': 'This is a test email.'
        }

        # Act
        result = email_handler.forward_email(incoming_email)

        # Assert
        self.assertFalse(result)
        mock_send_email.assert_called_once_with(
            to_addresses=['forwarded@example.com'],
            subject='Test Subject',
            body_html='This is a test email.',
            body_text='This is a test email.'
        )

Parameters

Parameter Details

bases: Inherits from unittest.TestCase, which provides the testing framework infrastructure including assertion methods (assertTrue, assertFalse) and test discovery mechanisms

Return Value

As a test class, it doesn't return values directly. Each test method executes assertions that either pass silently or raise AssertionError on failure. The unittest framework collects and reports test results.

Class Interface

Methods

Dependencies

• unittest
• forwarder.email_handler
• forwarder.o365_client

Required Imports

from unittest import TestCase
from unittest.mock import patch
from forwarder.email_handler import EmailHandler
from forwarder.o365_client import O365Client

Usage Example

import unittest
from unittest import TestCase
from unittest.mock import patch
from forwarder.email_handler import EmailHandler
from forwarder.o365_client import O365Client

class TestEmailHandler(TestCase):
    @patch.object(O365Client, 'send_email')
    def test_forward_email_success(self, mock_send_email):
        email_handler = EmailHandler()
        mock_send_email.return_value = True
        incoming_email = {
            'from': 'test@example.com',
            'to': 'forwarded@example.com',
            'subject': 'Test Subject',
            'body': 'This is a test email.'
        }
        result = email_handler.forward_email(incoming_email)
        self.assertTrue(result)

if __name__ == '__main__':
    unittest.main()

Best Practices

• This is a test class and should be run using a test runner (unittest, pytest) rather than instantiated directly
• Each test method is independent and uses the @patch decorator to mock external dependencies
• Tests follow the Arrange-Act-Assert pattern for clarity and maintainability
• Mock objects are configured before the code under test is executed to ensure predictable behavior
• The class tests both success and failure paths to ensure comprehensive coverage
• Test methods should be run in isolation; they don't depend on each other's state
• When adding new tests, follow the naming convention test_<method_name>_<scenario>
• Always verify both the return value and that mocked methods were called with expected parameters

Tags

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