CI on MacOS (#123)

Author: matthiasdiener

.github/workflows/test.yml

@@ -1,17 +1,18 @@
 name: Projections CI
 
-on: 
+on:
   pull_request: {}
   push:
     branches:
       - master
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
         java: [8, 11, 15]
+        os: [ubuntu-latest, macos-latest]
     steps:
       - uses: actions/checkout@v2
       - name: Set up JDK
@@ -21,4 +22,5 @@ jobs:
       - name: Build with Gradle
         run: gradle build
       - name: Run test
+        if: ${{ matrix.os == 'ubuntu-latest' }}
         run: xvfb-run -e /dev/stdout -a make test