diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..f4ed260
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,97 @@
+"""Pytest configuration and fixtures for dev-env-sync tests."""
+
+import os
+import tempfile
+from pathlib import Path
+from typing import Generator
+import pytest
+
+
+@pytest.fixture
+def temp_dir() -> Generator[Path, None, None]:
+    """Create a temporary directory for tests."""
+    with tempfile.TemporaryDirectory() as tmp:
+        yield Path(tmp)
+
+
+@pytest.fixture
+def sample_dotfile_content() -> str:
+    """Sample dotfile content."""
+    return "# Sample dotfile content\nexport TEST='value'\n"
+
+
+@pytest.fixture
+def sample_settings_json() -> str:
+    """Sample VS Code settings JSON."""
+    return '{\n  "editor.fontSize": 14,\n  "editor.tabSize": 2,\n  "files.autoSave": "afterDelay"\n}'
+
+
+@pytest.fixture
+def sample_config_yaml() -> str:
+    """Sample configuration YAML."""
+    return '''
+version: "1.0"
+name: "Test Environment"
+description: "Test configuration"
+
+dotfiles:
+  bashrc:
+    source: ./dotfiles/.bashrc
+    target: ~/.bashrc
+    backup: true
+  vimrc:
+    source: ./dotfiles/.vimrc
+    target: ~/.vimrc
+
+shell:
+  shell: bash
+  merge_strategy: replace
+
+editors:
+  vscode:
+    settings:
+      settings_file: ./editors/vscode/settings.json
+    extensions:
+      - name: ms-python.python
+
+packages:
+  - name: brew
+    packages:
+      - git
+      - neovim
+
+backup:
+  enabled: true
+  directory: ~/.dev-env-sync-backups
+  timestamp_format: "%Y%m%d_%H%M%S"
+'''
+
+
+@pytest.fixture
+def mock_platform_linux(mocker):
+    """Mock platform detection for Linux."""
+    mocker.patch('platform.system', return_value='Linux')
+    mocker.patch('platform.release', return_value='5.4.0')
+    mocker.patch('platform.version', return_value='#1 SMP')
+    mocker.patch('platform.machine', return_value='x86_64')
+    mocker.patch('pathlib.Path.home', return_value=Path('/home/testuser'))
+
+
+@pytest.fixture
+def mock_platform_macos(mocker):
+    """Mock platform detection for macOS."""
+    mocker.patch('platform.system', return_value='Darwin')
+    mocker.patch('platform.release', return_value='21.4.0')
+    mocker.patch('platform.version', return_value='Darwin Kernel Version 21.4.0')
+    mocker.patch('platform.machine', return_value='arm64')
+    mocker.patch('pathlib.Path.home', return_value=Path('/Users/testuser'))
+
+
+@pytest.fixture
+def mock_platform_wsl(mocker):
+    """Mock platform detection for WSL."""
+    mocker.patch('platform.system', return_value='Linux')
+    mocker.patch('platform.release', return_value='5.4.72-microsoft-standard-WSL2')
+    mocker.patch('platform.version', return_value='#1 SMP')
+    mocker.patch('platform.machine', return_value='x86_64')
+    mocker.patch('pathlib.Path.home', return_value=Path('/home/testuser'))