feat: Add comprehensive Python testing infrastructure

.gitignore

@@ -1,3 +1,42 @@
 *.pyc
 *.sublime-project
 *.sublime-workspace
+
+# Testing
+.pytest_cache/
+.coverage
+htmlcov/
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+
+# Poetry
+dist/
+
+# Virtual environments
+venv/
+.venv/
+env/
+.env/
+ENV/
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# Build artifacts
+build/
+__pycache__/
+*.egg-info/
+.eggs/
+
+# OS files
+.DS_Store
+Thumbs.db
+
+# Claude settings
+.claude/*

TESTING.md

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+# Testing Guide for Filter Lines
+
+This project uses Poetry for dependency management and pytest for testing.
+
+## Setup
+
+1. Install Poetry if you haven't already:
+   ```bash
+   curl -sSL https://install.python-poetry.org | python3 -
+   ```
+
+2. Install dependencies:
+   ```bash
+   poetry install --no-root
+   ```
+
+## Running Tests
+
+You can run tests in several ways:
+
+```bash
+# Run all tests
+poetry run pytest
+
+# Run with verbose output
+poetry run pytest -v
+
+# Run specific test file
+poetry run pytest tests/test_setup_validation.py
+
+# Run tests matching a pattern
+poetry run pytest -k "test_filter"
+
+# Run only unit tests
+poetry run pytest -m unit
+
+# Run only integration tests  
+poetry run pytest -m integration
+
+# Run tests excluding slow ones
+poetry run pytest -m "not slow"
+```
+
+## Coverage Reports
+
+The project is configured to generate coverage reports automatically:
+
+```bash
+# Run with coverage (default)
+poetry run pytest
+
+# View coverage in terminal
+poetry run pytest --cov-report=term
+
+# Generate HTML coverage report
+poetry run pytest --cov-report=html
+# Open htmlcov/index.html in your browser
+
+# Skip coverage
+poetry run pytest --no-cov
+```
+
+## Test Structure
+
+- `tests/` - Root test directory
+  - `conftest.py` - Shared pytest fixtures
+  - `unit/` - Unit tests (fast, isolated)
+  - `integration/` - Integration tests
+  - `test_setup_validation.py` - Validation tests for the testing infrastructure
+
+## Writing Tests
+
+1. Place unit tests in `tests/unit/`
+2. Place integration tests in `tests/integration/`
+3. Use the fixtures defined in `conftest.py` for mocking Sublime Text APIs
+4. Mark tests appropriately: `@pytest.mark.unit`, `@pytest.mark.integration`, `@pytest.mark.slow`
+
+## Available Fixtures
+
+See `tests/conftest.py` for all available fixtures:
+- `mock_sublime` - Mocked sublime module
+- `mock_sublime_plugin` - Mocked sublime_plugin module  
+- `mock_view` - Mocked Sublime Text view
+- `mock_window` - Mocked Sublime Text window
+- `temp_dir` - Temporary directory
+- `temp_file` - Create temporary files
+- `sample_text_lines` - Sample text content
+- `sample_config` - Sample configuration

pyproject.toml

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+[tool.poetry]
+name = "sublime-filter-lines"
+version = "3.1.4"
+description = "Quickly find all lines matching a string or regular expression in Sublime Text"
+authors = ["David Peckham <davidpeckham@users.noreply.github.com>"]
+license = "MIT"
+readme = "README.md"
+repository = "https://github.com/davidpeckham/sublime-filterlines"
+package-mode = false
+classifiers = [
+    "Development Status :: 5 - Production/Stable",
+    "Environment :: Plugins",
+    "Intended Audience :: Developers",
+    "License :: OSI Approved :: MIT License",
+    "Operating System :: OS Independent",
+    "Programming Language :: Python :: 3",
+    "Topic :: Text Editors"
+]
+
+[tool.poetry.dependencies]
+python = "^3.8"
+
+[tool.poetry.group.dev.dependencies]
+pytest = "^8.3.2"
+pytest-cov = "^5.0.0"
+pytest-mock = "^3.14.0"
+
+[tool.poe.tasks]
+test = "pytest"
+tests = "pytest"
+
+
+[tool.pytest.ini_options]
+minversion = "8.0"
+addopts = [
+    "-ra",
+    "--strict-markers",
+    "--strict-config",
+    "--cov=filter",
+    "--cov-branch",
+    "--cov-report=term-missing:skip-covered",
+    "--cov-report=html",
+    "--cov-report=xml",
+    "--cov-fail-under=80",
+]
+testpaths = ["tests"]
+python_files = ["test_*.py", "*_test.py"]
+python_classes = ["Test*"]
+python_functions = ["test_*"]
+markers = [
+    "unit: marks tests as unit tests (fast, isolated)",
+    "integration: marks tests as integration tests (may require external dependencies)",
+    "slow: marks tests as slow (deselect with '-m \"not slow\"')",
+]
+
+[tool.coverage.run]
+source = ["."]
+omit = [
+    "*/tests/*",
+    "*/__pycache__/*",
+    "*/venv/*",
+    "*/.venv/*",
+    "tests/*",
+]
+
+[tool.coverage.report]
+precision = 2
+show_missing = true
+skip_covered = false
+skip_empty = true
+exclude_lines = [
+    "pragma: no cover",
+    "def __repr__",
+    "if self.debug:",
+    "if settings.DEBUG",
+    "raise AssertionError",
+    "raise NotImplementedError",
+    "if 0:",
+    "if __name__ == .__main__.:",
+    "if TYPE_CHECKING:",
+    "class .*\\bProtocol\\):",
+    "@(abc\\.)?abstractmethod",
+]
+
+[tool.coverage.html]
+directory = "htmlcov"
+
+[tool.coverage.xml]
+output = "coverage.xml"
+
+[build-system]
+requires = ["poetry-core>=1.0.0"]
+build-backend = "poetry.core.masonry.api"

run_tests.sh

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+#!/bin/bash
+# Run tests using Poetry
+poetry run pytest "$@"