Add the macos workflow

.github/workflows/macos-tests.yml

@@ -0,0 +1,38 @@
+name: Test OS X Platform
+on:
+  pull_request:
+    branches:
+        - stable
+
+jobs:
+  Danger:
+    runs-on: macos-latest
+    env:
+      TEST_REPORTS: /tmp/test-results
+      LANG: en_US.UTF-8
+  
+    steps:
+      - uses: actions/checkout@v2
+      - name: Create Test Result Directory
+        run: mkdir -p $TEST_REPORTS
+      - name: Run Unit Test - macOS
+        run: |
+            cd XCode
+            set -o pipefail && xcodebuild test -scheme SwifterMac -sdk macosx -destination "arch=x86_64" | xcpretty -c -r html --output $TEST_REPORTS/macOS.html
+      - name: Run Unit Test - iOS
+        run: |
+            cd XCode
+            set -o pipefail && xcodebuild test -scheme SwifteriOS -sdk iphonesimulator -destination "name=iPhone 8" | xcpretty -c -r html --output $TEST_REPORTS/iOS.html
+      - name: Run Unit Test - tvOS
+        run: |
+            cd XCode
+            set -o pipefail && xcodebuild test -scheme SwiftertvOS -sdk appletvsimulator -destination "name=Apple TV 4K (at 1080p)" | xcpretty -c -r html --output $TEST_REPORTS/tvOS.html
+      - name: Run Unit Test - Swift Package Manager
+        run: |
+            cd XCode
+            swift build && swift test
+      - name: Archive Test results
+        uses: actions/upload-artifact@v1
+        with:
+            name: test-results
+            path: o/tmp/test-results