feat(converters): add Python unit test conversions (pytest, unittest, nose2)

[pmclSF]

Summary

Adds Python as the third supported language with 3 frameworks and 3 conversion directions. This is the architecture stress test — the first paradigm-crossing conversion in Hamlet: pytest is function-based (paradigm: 'function'), while unittest and nose2 are class-based (paradigm: 'xunit').

• pytest ↔ unittest: Bidirectional conversion between function-based and class-based test paradigms, including class wrapping/unwrapping, self parameter injection/removal, and assertion style translation
• nose2 → pytest: One-way migration from the legacy nose2 framework, converting nose-specific assertions and decorators to pytest equivalents
• 92 fixture tests covering assertions, structure, fixtures, markers, parametrize, imports, decorators, and unconvertible patterns

New Frameworks

Framework	File	Lines	Paradigm	Role
pytest	src/languages/python/frameworks/pytest.js	1031	function	Target for unittest→pytest and nose2→pytest
unittest	src/languages/python/frameworks/unittest_fw.js	937	xunit	Target for pytest→unittest
nose2	src/languages/python/frameworks/nose2.js	276	xunit	Source-only (detect/parse, stub emit)

Conversion Directions

pytest → unittest (9 phases)

1. Add import unittest
2. Wrap bare def test_*() in class TestXxx(unittest.TestCase):, indent 4 spaces, add self param
3. Convert @pytest.fixture(autouse=True) → setUp(self) / tearDown(self) (yield splits into both)
4. Convert bare assertions → self.assert* (~15 patterns)
5. Convert markers (@pytest.mark.skip → @unittest.skip, @pytest.mark.skipif → @unittest.skipIf, @pytest.mark.xfail → @unittest.expectedFailure)
6. @pytest.mark.parametrize → HAMLET-TODO (no direct equivalent)
7. Remove import pytest if no remaining references
8. Cleanup (indentation, blank lines)
9. Mark unconvertible (conftest fixtures, monkeypatch, capfd, tmp_path, capsys)

unittest → pytest (9 phases)

1. Remove import unittest / from unittest import TestCase
2. Add import pytest only when needed (assertRaises, fixtures, markers)
3. Strip class wrapper, dedent 4 spaces, remove self from signatures
4. Convert setUp/tearDown → @pytest.fixture(autouse=True) with yield
5. Convert self.assert* → bare assert (~20 patterns including assertAlmostEqual → pytest.approx, assertRaisesRegex → pytest.raises(match=))
6. Convert unittest decorators → pytest markers
7. Remove remaining import unittest
8. Cleanup
9. Mark unconvertible (setUpModule, tearDownModule, self.addCleanup, self.maxDiff)

nose2 → pytest (5 phases)

10. Remove nose imports (from nose.tools, import nose2)
11. Convert decorators (@params → @pytest.mark.parametrize, @attr → @pytest.mark)
12. Convert nose assertions → bare assert (assert_equal → assert ==, assert_raises → pytest.raises, etc.)
13. Add import pytest if needed
14. Mark unconvertible (nose2 plugins, layer decorators, such DSL)

Test Coverage (92 new tests)

pytest → unittest (37 tests)

Category	Count	Examples
structure/	8	Class wrapping, indentation, self param, docstrings, helper functions
assertions/	10	==, !=, assertTrue, assertFalse, isNone, in, isinstance, pytest.raises
fixtures/	6	autouse→setUp, yield→tearDown, non-autouse→TODO, session-scope→TODO
markers/	5	skip, skip(reason), skipif, xfail, custom marks
parametrize/	3	simple→TODO, multi-param→TODO, stacked→TODO
unconvertible/	5	conftest, monkeypatch, capfd, capsys, tmp_path

unittest → pytest (40 tests)

Category	Count	Examples
imports/	5	Remove unittest, add pytest conditionally, preserve other imports
structure/	8	Class unwrap, dedent, self removal, multiple classes, docstrings
assertions/	10	assertEqual→==, assertRaises→pytest.raises, assertIn→in, etc.
fixtures/	6	setUp→fixture, tearDown→yield, combined, multi-line bodies
markers/	4	skip, skipIf, skipUnless, expectedFailure
parametrize/	3	subTest passthrough, assertion conversion within subTest
unconvertible/	4	setUpModule, tearDownModule, addCleanup, maxDiff

nose2 → pytest (15 tests)

Category	Count	Examples
imports/	3	nose.tools removal, nose2 removal, pytest addition
assertions/	5	assert_equal, assert_true, assert_false, assert_raises, assert_in
decorators/	3	@params→parametrize, @attr→mark, combined decorators+assertions
unconvertible/	4	plugins, layer decorators, such DSL, test generators

Key Design Decisions

1. FRAMEWORK_FILE_OVERRIDE: New pattern in ConverterFactory to map unittest → unittest_fw.js filename (avoids Node reserved word issues). Framework name stays 'unittest' internally.

2. paradigm: 'function': New paradigm value for pytest, alongside existing 'bdd', 'bdd-e2e', 'xunit'.

3. No changes to ConversionPipeline.transform(): All conversion logic lives in emit() via regex on raw source, same pattern as Java converters.

4. splitArgs() utility: Handles nested parentheses in assertion arguments (e.g., self.assertEqual(foo(1), bar(2))). Shared between both emit functions.

5. Indentation-based class detection: Python class boundaries are detected via indent levels rather than brace counting.

Modified Files

• src/core/ConverterFactory.js: Added PYTEST/UNITTEST/NOSE2 to FRAMEWORKS, FRAMEWORK_LANGUAGE, PIPELINE_DIRECTIONS, getSupportedConversions (14 → 17 directions)
• test/core/ConverterFactory.test.js: Updated framework count (10 → 13), added 6 new tests (3 PipelineConverter creation + 3 conversion smoke tests)

Verification

Test Suites: 579 passed, 579 total
Tests:       1377 passed, 1377 total
npm run lint:  zero errors
npm run format: clean

Test plan

• All 1377 tests pass (1285 existing + 92 new)
• ESLint: zero errors
• Prettier: clean formatting
• ConverterFactory recognizes all 3 new frameworks (13 total)
• createConverter('pytest', 'unittest') returns PipelineConverter
• createConverter('unittest', 'pytest') returns PipelineConverter
• createConverter('nose2', 'pytest') returns PipelineConverter
• getSupportedConversions() returns 17 directions
• No changes to existing converter behavior (all pre-existing tests still pass)

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