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Testing Bridge Pattern Circle Drawing Implementation in python-patterns

This test suite validates the Bridge design pattern implementation in Python, focusing on drawing circle shapes with different API implementations. It verifies the separation between abstraction and implementation, allowing circle shapes to be drawn and scaled independently.

Test Coverage Overview

The test suite covers two main aspects of the Bridge pattern implementation:

Drawing circles using different concrete API implementations (DrawingAPI1 and DrawingAPI2)
Scaling circle shapes while maintaining independent implementation details
Verification of method calls and radius calculations across different implementations

Implementation Analysis

The testing approach utilizes unittest.mock.patch to isolate and verify interactions between components:

Mock objects verify correct method calls between CircleShape and DrawingAPI classes
Implementation details are tested through radius calculations and scaling operations
Separate test methods validate drawing and scaling functionality independently

Technical Details

Testing infrastructure includes:

Python’s unittest framework for test organization
unittest.mock.patch for method call verification
Class-level assertions (cls.assertEqual) for verification
Constants for test parameters and expected values

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolation of implementation details through mocking
Clear test method naming describing functionality under test
Separate test cases for different aspects of the pattern
Use of constants for test parameters and expected values
Verification of both method calls and state changes

faif/python-patterns

tests/structural/test_bridge.py

            
import unittest
from unittest.mock import patch

from patterns.structural.bridge import CircleShape, DrawingAPI1, DrawingAPI2


class BridgeTest(unittest.TestCase):
    def test_bridge_shall_draw_with_concrete_api_implementation(cls):
        ci1 = DrawingAPI1()
        ci2 = DrawingAPI2()
        with patch.object(ci1, "draw_circle") as mock_ci1_draw_circle, patch.object(
            ci2, "draw_circle"
        ) as mock_ci2_draw_circle:
            sh1 = CircleShape(1, 2, 3, ci1)
            sh1.draw()
            cls.assertEqual(mock_ci1_draw_circle.call_count, 1)
            sh2 = CircleShape(1, 2, 3, ci2)
            sh2.draw()
            cls.assertEqual(mock_ci2_draw_circle.call_count, 1)

    def test_bridge_shall_scale_both_api_circles_with_own_implementation(cls):
        SCALE_FACTOR = 2
        CIRCLE1_RADIUS = 3
        EXPECTED_CIRCLE1_RADIUS = 6
        CIRCLE2_RADIUS = CIRCLE1_RADIUS * CIRCLE1_RADIUS
        EXPECTED_CIRCLE2_RADIUS = CIRCLE2_RADIUS * SCALE_FACTOR

        ci1 = DrawingAPI1()
        ci2 = DrawingAPI2()
        sh1 = CircleShape(1, 2, CIRCLE1_RADIUS, ci1)
        sh2 = CircleShape(1, 2, CIRCLE2_RADIUS, ci2)
        sh1.scale(SCALE_FACTOR)
        sh2.scale(SCALE_FACTOR)
        cls.assertEqual(sh1._radius, EXPECTED_CIRCLE1_RADIUS)
        cls.assertEqual(sh2._radius, EXPECTED_CIRCLE2_RADIUS)
        with patch.object(sh1, "scale") as mock_sh1_scale_circle, patch.object(
            sh2, "scale"
        ) as mock_sh2_scale_circle:
            sh1.scale(2)
            sh2.scale(2)
            cls.assertEqual(mock_sh1_scale_circle.call_count, 1)
            cls.assertEqual(mock_sh2_scale_circle.call_count, 1)