Add test for a Gemfile depending on Bundler 1

.github/workflows/test.yml

@@ -111,7 +111,21 @@ jobs:
       with:
         ruby-version: 2.6
         bundler: 2.1.4
-    - run: bundle --version | grep -F 2.1.4
+    - run: bundle --version | grep -F "Bundler version 2.1.4"
+
+  testDependencyOnBundler1:
+    name: "Test gemfile depending on Bundler 1"
+    runs-on: ubuntu-latest
+    env:
+      BUNDLE_GEMFILE: gemfiles/bundler1.gemfile
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ./
+        with:
+          ruby-version: 2.7
+          bundler: 1
+          bundler-cache: true
+      - run: bundle --version | grep -F "Bundler version 1."
 
   testGemfileMatrix:
     strategy: