Add tests

.github/workflows/ci.yml

@@ -7,10 +7,12 @@ on:
 
 jobs:
   test:
-    name: Test (Node ${{ matrix.node-version }})
-    runs-on: ubuntu-latest
+    name: Test (Node ${{ matrix.node-version }}, ${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
     strategy:
+      fail-fast: false
       matrix:
+        os: [ubuntu-latest, windows-latest]
         node-version: [24, 25]
 
     steps:
@@ -34,3 +36,6 @@ jobs:
 
       - name: Build
         run: node --run build
+
+      - name: Run tests
+        run: node --run test

.github/workflows/release.yml

@@ -26,6 +26,7 @@ jobs:
         uses: actions/setup-node@v6
         with:
           node-version: 25
+          check-latest: true
           registry-url: 'https://registry.npmjs.org'
 
       - name: Install dependencies
@@ -40,6 +41,9 @@ jobs:
       - name: Build
         run: node --run build
 
+      - name: Run tests
+        run: node --run test
+
       - name: Update version
         run: |
           git config user.name "${{ github.actor }}"

.gitignore

@@ -1,3 +1,4 @@
 /.cache
 /dist
 /node_modules
+/coverage

README.md

@@ -11,7 +11,7 @@ The plugin does not process the CSS in any way whatsoever, it is merely output i
 
 ## Installation
 
-```
+```bash
 npm install -D ecij
 ```
 
@@ -133,9 +133,43 @@ ecij({
 });
 ```
 
+## Development
+
+### Building
+
+```bash
+npm run build
+```
+
+### Formatting
+
+```bash
+npm run format
+```
+
+### Type Checking
+
+```bash
+npm run typecheck
+```
+
+### Running Tests
+
+The project uses **integration tests** with **inline snapshot testing** to validate transformations.
+
+```bash
+# Run tests once
+npm test
+
+# Run tests with coverage
+npm run test:coverage
+
+# Update inline snapshots after intentional changes
+npm test -- -u
+```
+
 ## TODO
 
-- Tests
 - Scope handling
 - Validate that the `css` used refers to the ecij export
 - Full import/export handling (default/namespace import/export)