Rebuild container child lifecycle

Assisted-By: devx/a01026a8-dd63-4b91-bae4-aec7ee8f7fa3

Author: samuel-williams-shopify

fixtures/async/container/a_child.rb

@@ -0,0 +1,156 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2026, by Samuel Williams.
+
+module Async
+	module Container
+		AChild = Sus::Shared("a child") do
+			def wait_until_ready(input)
+				input.gets
+			end
+			
+			def start_ready_child
+				subject.call(name: "test-child") do |instance|
+					instance.ready!(status: "ready")
+				end
+			end
+			
+			def start_sleeping_child
+				ready = ::IO.pipe
+				
+				child = subject.call(name: "test-child") do
+					ready.last.puts "ready"
+					sleep
+				rescue Interrupt
+					# Graceful shutdown.
+				end
+				
+				wait_until_ready(ready.first)
+				
+				return child
+			end
+			
+			def start_uncooperative_child
+				ready = ::IO.pipe
+				
+				child = subject.call(name: "test-child") do
+					ready.last.puts "ready"
+					
+					loop do
+						begin
+							sleep
+						rescue Interrupt
+							# Ignore graceful shutdown.
+						end
+					end
+				end
+				
+				wait_until_ready(ready.first)
+				
+				return child
+			end
+			
+			it "receives notifications and returns a successful status" do
+				child = start_ready_child
+				
+				messages = []
+				status = child.wait do |message|
+					messages << message
+				end
+				
+				expect(messages).to be == [{ready: true, status: "ready"}]
+				expect(status).to be(:success?)
+			end
+			
+			it "tracks when the child last sent a message" do
+				child = start_ready_child
+				last_updated_at = child.last_updated_at
+				
+				messages = []
+				child.wait do |message|
+					messages << message
+				end
+				
+				expect(messages).to be == [{ready: true, status: "ready"}]
+				expect(child.last_updated_at).to be >= last_updated_at
+			end
+			
+			it "can receive messages until the child is ready" do
+				child = subject.call(name: "test-child") do |instance|
+					instance.ready!(status: "ready")
+					sleep
+				rescue Interrupt
+					# Graceful shutdown.
+				end
+				
+				result = child.receive do
+					break :ready if child.ready?
+				end
+				
+				expect(result).to be == :ready
+				expect(child).to be(:ready?)
+				
+				status = child.stop(true)
+				
+				expect(status).to be(:success?)
+			end
+			
+			it "returns a successful status for normal exit" do
+				child = subject.call(name: "test-child") do
+					# Exit normally.
+				end
+				
+				status = child.wait
+				
+				expect(status).to be(:success?)
+			end
+			
+			it "returns nil when wait times out" do
+				child = start_sleeping_child
+				last_updated_at = child.last_updated_at
+				
+				expect(child.wait(0.001)).to be_nil
+				expect(child.last_updated_at).to be == last_updated_at
+				
+				status = child.stop(false)
+				
+				expect(status).not.to be(:success?)
+			end
+			
+			it "can stop gracefully" do
+				child = start_sleeping_child
+				
+				status = child.stop(true)
+				
+				expect(status).to be(:success?)
+			end
+			
+			it "can kill immediately" do
+				child = start_sleeping_child
+				
+				status = child.stop(false)
+				
+				expect(status).not.to be(:success?)
+			end
+			
+			it "kills the child when graceful shutdown times out" do
+				child = start_uncooperative_child
+				
+				status = child.stop(0.001)
+				
+				expect(status).not.to be(:success?)
+			end
+			
+			it "returns a failure status when the child fails" do
+				child = subject.call(name: "test-child") do
+					raise "boom"
+				end
+				
+				status = child.wait
+				
+				expect(status).not.to be(:success?)
+			end
+		end
+	end
+end