Add tests for controller restart behaviour.

Assisted-By: devx/904563b8-dbee-48b0-9726-f036df3ed96d

Author: samuel-williams-shopify

test/async/container/controller.rb

@@ -84,6 +84,87 @@ def controller.setup(container)
 		end
 	end
 
+	with "#restart" do
+		it "replaces the running container with a new one" do
+			def controller.setup(container)
+				container.spawn do |instance|
+					instance.ready!
+					sleep
+				end
+			end
+			
+			controller.start
+			first = controller.container
+			
+			expect(first).not.to be_nil
+			expect(controller).to be(:running?)
+			
+			# A restart is a blue-green swap: a new container is created and the old one is stopped.
+			controller.restart
+			
+			expect(controller.container).not.to be_equal(first)
+			expect(controller).to be(:running?)
+		ensure
+			controller.stop(false)
+		end
+		
+		it "starts a new container if not already running" do
+			def controller.setup(container)
+				container.spawn do |instance|
+					instance.ready!
+					sleep
+				end
+			end
+			
+			expect(controller).not.to be(:running?)
+			
+			controller.restart
+			
+			expect(controller).to be(:running?)
+			expect(controller.container).not.to be_nil
+		ensure
+			controller.stop(false)
+		end
+		
+		it "restarts when Restart is raised into the running controller thread" do
+			def controller.setup(container)
+				container.spawn do |instance|
+					instance.ready!
+					sleep
+				end
+			end
+			
+			# Run the controller in a thread so we can deliver `Restart` via `Thread#raise`, which is the in-process (cross-thread) analog of sending `SIGHUP` to a process running a controller. `Child#restart!` uses exactly this mechanism.
+			thread = Thread.new do
+				Thread.current.report_on_exception = false
+				controller.run
+			end
+			
+			# Wait until the controller is running:
+			10.times do
+				break if controller.running?
+				sleep 0.1
+			end
+			expect(controller).to be(:running?)
+			
+			first = controller.container
+			
+			thread.raise(Async::Container::Restart)
+			
+			# Wait until the container has been replaced by the restart:
+			10.times do
+				break if controller.container && !controller.container.equal?(first)
+				sleep 0.1
+			end
+			
+			expect(controller.container).not.to be_equal(first)
+			expect(controller).to be(:running?)
+		ensure
+			thread&.raise(Async::Container::Interrupt)
+			thread&.join
+		end
+	end
+	
 	with "notify" do
 		before do
 			@notify_server = Async::Container::Notify::Server.open