Add tests for ActiveSupportEventReporter integration

Adds tests for the hook and integration, structured to handle both
Rails 8.1+ (where ActiveSupport::EventReporter is available) and
earlier versions (where it's not).

Author: jeffkreeftmeijer

spec/lib/appsignal/hooks/active_support_event_reporter_spec.rb

@@ -0,0 +1,53 @@
+describe Appsignal::Hooks::ActiveSupportEventReporterHook do
+  begin
+    require "active_support/event_reporter"
+  rescue LoadError
+  end
+
+  describe "#dependencies_present?" do
+    subject { described_class.new.dependencies_present? }
+
+    if defined?(::ActiveSupport::EventReporter)
+      context "when ActiveSupport::EventReporter is present" do
+        it { is_expected.to be_truthy }
+      end
+    else
+      context "when ActiveSupport::EventReporter is not present" do
+        it { is_expected.to be_falsy }
+      end
+    end
+  end
+
+  if defined?(::ActiveSupport::EventReporter)
+    describe "#install" do
+      before do
+        # Mock Rails.event
+        stub_const("MockEventReporter", Class.new do
+          attr_reader :subscribers
+
+          def initialize
+            @subscribers = []
+          end
+
+          def subscribe(subscriber)
+            @subscribers << subscriber
+          end
+        end)
+
+        mock_event_reporter = MockEventReporter.new
+
+        allow(Rails).to receive(:event).and_return(mock_event_reporter)
+      end
+
+      it "subscribes the ActiveSupportEventReporter::Subscriber to Rails.event" do
+        event_reporter = Rails.event
+        expect(event_reporter.subscribers).to be_empty
+
+        described_class.new.install
+
+        expect(event_reporter.subscribers.length).to eq(1)
+        expect(event_reporter.subscribers.first).to be_a(Appsignal::Integrations::ActiveSupportEventReporter::Subscriber)
+      end
+    end
+  end
+end

spec/lib/appsignal/integrations/active_support_event_reporter_spec.rb

@@ -0,0 +1,24 @@
+require "appsignal/integrations/active_support_event_reporter"
+
+describe Appsignal::Integrations::ActiveSupportEventReporter::Subscriber do
+  let(:subscriber) { described_class.new }
+  let(:logger) { instance_double(Appsignal::Logger) }
+
+  before do
+    start_agent
+    allow(Appsignal::Logger).to receive(:new).with("rails_events").and_return(logger)
+  end
+
+  describe "#emit" do
+    it "logs the event name and payload" do
+      event = {
+        :name => "user.created",
+        :payload => { :id => 123, :email => "user@example.com" },
+      }
+
+      expect(logger).to receive(:info).with("user.created", { :id => 123, :email => "user@example.com" })
+
+      subscriber.emit(event)
+    end
+  end
+end