Pin CI actions and test Ruby 4

.github/workflows/release.yml

@@ -14,11 +14,11 @@ jobs:
       id-token: write
     environment: release
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5.0.1
         with:
           persist-credentials: false
-      - uses: ruby/setup-ruby@v1
+      - uses: ruby/setup-ruby@003a5c4d8d6321bd302e38f6f0ec593f77f06600 # v1.319.0
         with:
           ruby-version: ruby
           bundler-cache: true
-      - uses: rubygems/release-gem@v1
+      - uses: rubygems/release-gem@052cc82692552de3ef2b81fd670e41d13cba8092 # v1.4.0

.github/workflows/test.yml

@@ -12,12 +12,12 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ["3.2", "3.3", "3.4"]
+        ruby: ["3.2", "3.3", "3.4", "4.0"]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5.0.1
 
       - name: Set up Ruby ${{ matrix.ruby }}
-        uses: ruby/setup-ruby@v1
+        uses: ruby/setup-ruby@003a5c4d8d6321bd302e38f6f0ec593f77f06600 # v1.319.0
         with:
           ruby-version: ${{ matrix.ruby }}
           bundler-cache: true

test/release_workflow_test.rb

@@ -6,6 +6,7 @@ require "yaml"
 class ReleaseWorkflowTest < Minitest::Test
   ROOT = File.expand_path("..", __dir__)
   WORKFLOW_PATH = File.join(ROOT, ".github", "workflows", "release.yml")
+  RELEASE_GEM_ACTION = "rubygems/release-gem@052cc82692552de3ef2b81fd670e41d13cba8092"
 
   def workflow
     @workflow ||= YAML.safe_load(File.read(WORKFLOW_PATH), aliases: false)
@@ -27,7 +28,7 @@ class ReleaseWorkflowTest < Minitest::Test
     )
 
     steps = push_job.fetch("steps")
-    assert_equal 1, steps.count { |step| step["uses"] == "rubygems/release-gem@v1" }
+    assert_equal 1, steps.count { |step| step["uses"] == RELEASE_GEM_ACTION }
     refute steps.any? { |step| step.fetch("run", "").match?(/\bgem\s+push\b/) }
   end
 end

test/workflow_contract_test.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+require "minitest/autorun"
+require "yaml"
+
+class WorkflowContractTest < Minitest::Test
+  ROOT = File.expand_path("..", __dir__)
+  WORKFLOW_DIRECTORY = File.join(ROOT, ".github", "workflows")
+  TEST_WORKFLOW_PATH = File.join(WORKFLOW_DIRECTORY, "test.yml")
+  ACTION_PINS = {
+    "actions/checkout" => "93cb6efe18208431cddfb8368fd83d5badbf9bfd",
+    "ruby/setup-ruby" => "003a5c4d8d6321bd302e38f6f0ec593f77f06600",
+    "rubygems/release-gem" => "052cc82692552de3ef2b81fd670e41d13cba8092"
+  }.freeze
+
+  def test_matrix_covers_every_supported_ruby
+    workflow = YAML.safe_load(File.read(TEST_WORKFLOW_PATH), aliases: false)
+    versions = workflow.dig("jobs", "test", "strategy", "matrix", "ruby")
+
+    assert_equal %w[3.2 3.3 3.4 4.0], versions
+  end
+
+  def test_every_third_party_action_uses_its_reviewed_commit
+    action_uses = Dir[File.join(WORKFLOW_DIRECTORY, "*.{yml,yaml}")].sort.flat_map do |path|
+      File.readlines(path).filter_map do |line|
+        line[/^\s*-?\s*uses:\s*([^\s#]+)/, 1]
+      end
+    end
+
+    assert_equal 5, action_uses.length
+    action_uses.each do |action_use|
+      action, separator, revision = action_use.rpartition("@")
+
+      assert_equal "@", separator
+      assert_equal ACTION_PINS.fetch(action), revision
+      assert_match(/\A[0-9a-f]{40}\z/, revision)
+    end
+  end
+end