add a "dart test" test

.github/workflows/dart.yml

@@ -89,3 +89,28 @@ jobs:
           stagehand console-simple
           dart pub get
           dart run
+
+  test_test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        # Test latest stable, beta, dev channels
+        sdk: [stable, beta, dev]
+        flavor: [release]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ./
+        with:
+          sdk: ${{ matrix.sdk }}
+
+      - id: dart_pub_upgrade
+        name: Dart pub upgrade
+        working-directory: example
+        run: dart pub upgrade
+
+      - name: Dart test
+        if: "always() && steps.dart_pub_upgrade.conclusion == 'success'"
+        working-directory: example
+        run: dart test

.gitignore

@@ -0,0 +1,3 @@
+example/.packages
+example/pubspec.lock
+example/.dart_tool/

example/pubspec.yaml

@@ -0,0 +1,6 @@
+name: example
+publish_to: none
+environment:
+  sdk: '>=2.12.0 <3.0.0'
+dev_dependencies:
+  test: any

example/test/example_test.dart

@@ -0,0 +1,11 @@
+// Copyright (c) 2021, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:test/test.dart';
+
+void main() {
+  test('true is true', () {
+    expect(true, isTrue);
+  });
+}