Add Rails integration test

test/integration/rails_integration_test.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "tempfile"
+require "fileutils"
+require "open3"
+
+class RailsIntegrationTest < ActiveSupport::TestCase
+  CommandFailed = Class.new(StandardError)
+
+  test "running a job in a Rails app works" do
+    in_dummy_rails_app_with_job_iteration do |dir|
+      File.write("app/jobs/example_job.rb", <<~RUBY)
+        class ExampleJob < ApplicationJob
+          include JobIteration::Iteration
+
+          def build_enumerator(cursor:)
+            enumerator_builder.array(["it works"], cursor: cursor)
+          end
+
+          def each_iteration(string)
+            puts string
+          end
+        end
+      RUBY
+
+      output = run_or_raise("bin/rails", "runner", "ExampleJob.perform_now")
+      assert_includes(output, "it works")
+    end
+  end
+
+  private
+
+  def in_dummy_rails_app_with_job_iteration
+    Dir.mktmpdir do |dir|
+      Dir.chdir(dir) do |dir|
+        dir = File.join(dir, "dummy")
+        FileUtils.mkdir(dir)
+        Dir.chdir(dir) do |dir|
+          Bundler.with_unbundled_env do
+            run_or_raise("bundle", "init")
+            run_or_raise("bundle", "add", "rails", "--version", rails_version.to_s)
+            run_or_raise("rails", "new", ".", "--force")
+            run_or_raise("bundle", "add", "job-iteration")
+
+            yield dir
+          end
+        end
+      end
+    end
+  end
+
+  def run_or_raise(*args, **kwargs, &block)
+    stdout_and_stderr_str, status = Open3.capture2e(*args, **kwargs, &block)
+    raise CommandFailed, stdout_and_stderr_str unless status.success?
+
+    stdout_and_stderr_str
+  end
+
+  def rails_version
+    # We're going to install Rails in the dummy app, so we need to know the version to install.
+    # We don't depend on Rails though, so read the version of Active Support instead, since they always match.
+    Gem.loaded_specs.fetch("activesupport").version
+  end
+end