[python] Migrate to Pytest

[hayat01sh1da]

1. Problem Overview

Running pytest . in the coding-tests/python directory produced 6 ModuleNotFoundError import failures:

ERROR collecting calculator_cli_app/test/queries/test_calculation_query.py
ERROR collecting calculator_cli_app/test/test_application.py
ERROR collecting fibonacci_sequence/test/test_fibonacci.py
ERROR collecting fizzbuzz/test/test_fizzbuzz.py
ERROR collecting letter_inspection/test/test_application.py
ERROR collecting nabeatsu/test/test_nabeatsu.py

2. Root Causes

1. Incorrect Relative Paths: Test files used sys.path.append('./src') assuming execution from the project root, but pytest runs from individual test module directories
2. Module Name Collisions: Multiple packages had identically named modules:
   • calculator_cli_app/src/application.py vs letter_inspection/src/application.py
   • calculator_cli_app/test/test_application.py vs letter_inspection/test/test_application.py
3. Global sys.path Pollution: calculator_cli_app/src/application.py had global sys.path.append() statements that interfered with other modules
4. Module Caching: Python's module cache reused previously imported modules with the same name, causing signature mismatches

3. Solutions Implemented

3-1. Fixed Import Paths in All Test Files

Updated 6 test files to use __file__-based absolute paths:

Files Updated:

• calculator_cli_app/test/test_application.py
• calculator_cli_app/test/queries/test_calculation_query.py
• fibonacci_sequence/test/test_fibonacci.py
• fizzbuzz/test/test_fizzbuzz.py
• letter_inspection/test/test_letter_inspection_application.py
• nabeatsu/test/test_nabeatsu.py

Pattern Applied:

test_dir = os.path.dirname(os.path.abspath(__file__))
module_root = os.path.dirname(test_dir)
src_path = os.path.join(module_root, 'src')

# Clear cached modules
for mod in list(sys.modules.keys()):
    if mod == 'application':
        del sys.modules[mod]

if src_path not in sys.path:
    sys.path.insert(0, src_path)

from application import Application

3-2. Added Module Cache Clearing

Before each import, cleared cached modules to prevent cross-module interference:

for mod in list(sys.modules.keys()):
    if mod == 'application':
        del sys.modules[mod]

This ensures each test imports the correct application.py from its own package directory.

3-3. Renamed Duplicate Test File

Renamed letter_inspection/test/test_application.py to letter_inspection/test/test_letter_inspection_application.py to avoid pytest module name collision.

3-4. Removed Global sys.path Modifications

Removed problematic code from calculator_cli_app/src/application.py:

# REMOVED:
import sys
sys.path.append('./calculator_cli_app/src')
sys.path.append('./calculator_cli_app/src/lib')
sys.path.append('./calculator_cli_app/src/queries')
sys.path.append('./calculator_cli_app/src/validations')

Dependencies are now handled through proper test-level sys.path management.

3-5. Added all Exports

Added explicit __all__ definitions to modules with wildcard imports:

• fizzbuzz/src/fizzbuzz.py: __all__ = ['fizzbuzz_in_if', 'fizzbuzz_in_ternary']
• nabeatsu/src/nabeatsu.py: __all__ = ['go_crazy_in_if', 'go_crazy_in_ternary']
• fibonacci_sequence/src/fibonacci.py: __all__ = ['fibonacci']

3-6. Updated pyproject.toml

Added pytest configuration to properly handle module discovery:

[tool.pytest.ini_options]
python_files = ["test_*.py"]
python_classes = ["Test*"]
python_functions = ["test_*"]

4. Results

✅ All 12 tests now pass successfully

calculator_cli_app/test/queries/test_calculation_query.py::TestArgumentZero::test_f_with_zero PASSED
calculator_cli_app/test/queries/test_calculation_query.py::TestArgumentTwo::test_f_with_two PASSED
calculator_cli_app/test/queries/test_calculation_query.py::TestArgumentFour::test_f_with_four PASSED
calculator_cli_app/test/test_application.py::TestApplication::test_run_success PASSED
fibonacci_sequence/test/test_fibonacci.py::TestCase1::test_fibonacci PASSED
fibonacci_sequence/test/test_fibonacci.py::TestCase2::test_fibonacci PASSED
fizzbuzz/test/test_fizzbuzz.py::TestIfStatement::test_fizzbuzz PASSED
fizzbuzz/test/test_fizzbuzz.py::TestTernaryStatement::test_fizzbuzz PASSED
letter_inspection/test/test_letter_inspection_application.py::TestRegularCase::test_exactly_equal_size_and_included_1 PASSED
letter_inspection/test/test_letter_inspection_application.py::TestCase1::test_exactly_equal_size_and_included_3 PASSED
nabeatsu/test/test_nabeatsu.py::TestIfStatement::test_go_crazy PASSED
nabeatsu/test/test_nabeatsu.py::TestTernaryStatement::test_go_crazy PASSED

12 passed in 4.24s

5. Key Takeaways

• Always use __file__-based paths for test imports, not working directory-relative paths
• Clear module cache when importing identically-named modules from different packages
• Avoid global sys.path modifications in source files
• Use explicit __all__ definitions for wildcard imports
• Ensure unique test file names to prevent pytest module collision issues