Run unit tests on an Android emulator in CI

Nested virtualization for the emulator isn't available on the
macOS runner used for the build job, so this runs on ubuntu-latest
via the swift-android-action, pinned to the same SDK artifact
bundle already used for building.

Author: colemancda

.github/workflows/swift.yml

@@ -66,3 +66,24 @@ jobs:
           bash "$HOME/Library/org.swift.swiftpm/swift-sdks/swift-${{ env.SWIFT_VERSION }}-RELEASE_android.artifactbundle/swift-android/scripts/setup-android-sdk.sh"
     - name: Build
       run: swift build --swift-sdk aarch64-unknown-linux-android28 -c ${{ matrix.config }}
+
+  android-test:
+    name: Android Test
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        config: ["debug", "release"]
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+    - name: Test on Android emulator
+      uses: skiptools/swift-android-action@v2
+      with:
+        swift-version: "6.3.2"
+        custom-sdk-id: swift-6.3.2-RELEASE_android
+        custom-sdk-url: https://download.swift.org/swift-6.3.2-release/android-sdk/swift-6.3.2-RELEASE/swift-6.3.2-RELEASE_android.artifactbundle.tar.gz
+        android-api-level: 28
+        swift-configuration: ${{ matrix.config }}
+        free-disk-space: true
+        run-tests: true