feat: test each postcss major version

packages/postcss-if-function/.npmignore

@@ -1,3 +1,5 @@
 /*
 /*/
 !/dist/
+examples/
+scripts/

packages/postcss-if-function/README.md

@@ -259,7 +259,7 @@ module.exports = {
 
 - **Style Functions Not Supported**: This plugin only transforms `media()` and `supports()` functions. For `style()` functions (which depend on runtime DOM state), use the [css-if-polyfill](https://github.com/mfranzke/css-if-polyfill/tree/main/packages/css-if-polyfill/) runtime (browser) library
 - **Static Analysis Only**: The plugin performs static analysis and cannot handle dynamically generated CSS
-- **PostCSS Compatibility**: Requires PostCSS 8.0.0 or higher
+- **PostCSS Compatibility**: Compatible with PostCSS 7 and 8. Automatically detects and adapts to the PostCSS version in use.
 
 ## Integration with Runtime Polyfill
 

packages/postcss-if-function/examples/README.md

@@ -0,0 +1,61 @@
+# PostCSS Version Compatibility Testing
+
+This directory contains test environments for different major versions of PostCSS to ensure our plugin works across multiple versions.
+
+## Structure
+
+- `postcss-version-7/` - Test environment for PostCSS v7.x
+- `postcss-version-8/` - Test environment for PostCSS v8.x
+
+Each directory contains:
+
+- `package.json` - Specific PostCSS version dependency
+- `test.test.js` - Test suite with comprehensive functionality tests
+- `vitest.config.js` - Test configuration with version-specific environment
+
+## Usage
+
+### Run all version tests
+
+```bash
+npm run test:versions
+```
+
+### Run specific version tests
+
+```bash
+npm run test:version-7
+npm run test:version-8
+```
+
+### Update peer dependencies package.json entry based on test results
+
+```bash
+npm run update:peer-deps
+```
+
+## How it works
+
+1. Each test environment runs the same comprehensive test suite against different PostCSS versions
+2. Tests verify core functionality: media() and supports() transformations, complex queries, comments handling, etc.
+3. The `update:peer-deps` script runs all version tests and updates the `peerDependencies` field in package.json based on which versions pass
+4. This ensures the peerDependencies range only includes actually tested and working versions
+5. The plugin automatically detects and adapts to the PostCSS version being used
+
+## Adding new PostCSS versions
+
+To add support for a new PostCSS version:
+
+1. Create a new directory: `postcss-version-X/`
+2. Copy the structure from an existing version directory
+3. Update the PostCSS version in the new `package.json`
+4. Update the version number in `vitest.config.js`
+5. Add the new version to the `versions` array in `../scripts/update-peer-deps.js`
+6. Add a test script in the main `package.json`
+
+## Current Compatibility
+
+✅ **PostCSS 7.x** - Fully supported
+✅ **PostCSS 8.x** - Fully supported
+
+The plugin uses a hybrid approach that automatically detects the PostCSS version and adapts its API usage accordingly.