Test multiple rubies

.github/workflows/ruby.yml

@@ -3,18 +3,20 @@ name: Ruby
 on: [push]
 
 jobs:
-  build:
-
+  test:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby_version: [2.4.x, 2.5.x, 2.6.x]
 
     steps:
     - uses: actions/checkout@v1
-    - name: Set up Ruby 2.6
+    - name: Set up Ruby ${{ matrix.ruby_version }}
       uses: actions/setup-ruby@v1
       with:
-        ruby-version: 2.6.x
+        ruby-version: ${{ matrix.ruby_version }}
     - name: Build and test with Rake
       run: |
         gem install bundler -v 1.16
         bundle install --jobs 4 --retry 3
-        bundle exec rake
+        bundle exec rspec