action: test on windows with a build matrix

.github/workflows/test.yml

@@ -1,21 +1,27 @@
 name: Node CI
 
-on: [push]
+on: [push, pull_request]
 
 jobs:
   build:
-
-    runs-on: ubuntu-latest
-
     strategy:
       matrix:
-        node-version: [8.x, 10.x, 12.x]
-
+        node: [8.x, 10.x, 12.x]
+        os: [ubuntu-latest, windows-latest]
+        cmd: [npm cit]
+        exclude: # only test windows on node 12
+          - os: windows-latest
+            node: 8.x
+          - os: windows-latest
+            node: 10.x
+          - os: windows-latest
+            node: 12.x
+    runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v1
-    - name: Use Node.js ${{ matrix.node-version }}
+    - name: Use Node.js ${{ matrix.node }}
       uses: actions/setup-node@v1
       with:
-        node-version: ${{ matrix.node-version }}
-    - name: npm install and test
-      run: npm cit
+        node-version: ${{ matrix.node }}
+    - name: ${{ matrix.cmd }}
+      run: ${{ matrix.cmd }}