Test all virtual environments, not just the latest, and added crontab (#60)

.github/workflows/test.yml

@@ -8,25 +8,31 @@ on:
     - '*'
     paths-ignore:
     - README.md
+  schedule:
+    - cron: '0 7 * * SUN'
 jobs:
   test:
     strategy:
       fail-fast: false
       matrix:
-        os: [ ubuntu, macos, windows ]
+        os: [ ubuntu-16.04, ubuntu-18.04, ubuntu-20.04, macos-10.15, windows-2016, windows-2019 ]
         # Use various version syntax here for testing
         ruby: [ 2.2, 2.3, 2.4, 2.5, 2.6.6, 2.7, ruby-head, debug, jruby-9.1, jruby, jruby-head, truffleruby, truffleruby-head ]
         include:
-        - { os: ubuntu, ruby: rubinius }
-        - { os: windows, ruby: mingw }
-        - { os: windows, ruby: mswin }
+        - { os: ubuntu-18.04, ruby: rubinius }
+        - { os: windows-2016, ruby: mingw }
+        - { os: windows-2019, ruby: mingw }
+        - { os: windows-2019, ruby: mswin }
         exclude:
-        - { os: windows, ruby: debug }
-        - { os: windows, ruby: truffleruby }
-        - { os: windows, ruby: truffleruby-head }
+        - { os: windows-2016, ruby: debug }
+        - { os: windows-2016, ruby: truffleruby }
+        - { os: windows-2016, ruby: truffleruby-head }
+        - { os: windows-2019, ruby: debug }
+        - { os: windows-2019, ruby: truffleruby }
+        - { os: windows-2019, ruby: truffleruby-head }
 
     name: ${{ matrix.os }} ${{ matrix.ruby }}
-    runs-on: ${{ matrix.os }}-latest
+    runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v2
 
@@ -39,7 +45,7 @@ jobs:
       run: |
         ruby -e "puts 'build compiler: ' + RbConfig::CONFIG.fetch('CC_VERSION_MESSAGE', 'unknown').lines.first"
     - name: gcc and ridk version (mingw)
-      if: matrix.os == 'windows'
+      if: startsWith(matrix.os, 'windows')
       run: |
         $abi, $plat = $(ruby -e "STDOUT.write RbConfig::CONFIG['ruby_version'] + ' ' + RUBY_PLATFORM").split(' ')
         if ($plat.Contains('mingw')) {
@@ -65,10 +71,10 @@ jobs:
     - run: bundle exec rake --version
 
     - name: which ruby, rake
-      if: matrix.os != 'windows'
+      if: "!startsWith(matrix.os, 'windows')"
       run: which -a ruby rake
     - name: where ruby, rake
-      if: matrix.os == 'windows'
+      if: startsWith(matrix.os, 'windows')
       run: |
         $ErrorActionPreference = 'Continue'
         $where = 'ruby', 'rake'