Add comprehensive test suite with GitHub Actions CI/CD integration

[Copilot]

Implements pytest-based test infrastructure with multi-version Python CI/CD pipeline. No external coverage services.

Test Suite

tests/test_main.py (25 tests, 51% coverage on main.py):

• Muscle group selection (numeric and text input)
• CLI commands (list, start, next, skip, end, stats, video, help, license, quit)
• Workout flow integration tests
• Input validation and error handling

tests/test_gui.py (5 tests):

• GUI component initialization
• Percentage calculations
• Graceful skip in headless environments

Example test pattern:

@patch('builtins.print')
@patch('builtins.input')
def test_abs_selection_by_name(mock_input, mock_print):
    mock_input.side_effect = ['abs', 'quit']
    with pytest.raises(SystemExit):
        main.workout()
    printed_output = [str(call) for call in mock_print.call_args_list]
    assert any('Ab muscle group selected' in str(call) for call in printed_output)

GitHub Actions Workflow

.github/workflows/tests.yml:

• Matrix testing: Python 3.9-3.12
• Coverage reports (HTML, XML, terminal) with artifacts
• Coverage summary in Actions UI
• Integrated pylint check
• Triggers: push/PR to main, develop

Configuration

• requirements.txt: pytest, pytest-cov, pytest-mock
• setup.cfg: pytest config with coverage settings
• tests/README.md: usage, writing guidelines, troubleshooting

Results: 25 passing tests, 5 skipped (GUI), 55% overall coverage, 0 security vulnerabilities (CodeQL).

Original prompt

Create a comprehensive test suite with a GitHub Actions integration. DO NOT use Codecov.

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[github-actions]

Thank you for your contribution, please read and sign our CLA. Instructions on how to do so can be found in the CONTRIBUTING.md document.

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I have read the CLA Document, and I hereby sign the CLA.

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