Add tests.

test/async/task.rb

@@ -17,6 +17,32 @@ def after
 		super
 	end
 
+	with '#annotate' do
+		it "can annotate the current task that has not started yet" do
+			task = Async::Task.new(reactor) do |task|
+				sleep
+			end
+
+			task.annotate("Hello World")
+
+			expect(task.annotation).to be == "Hello World"
+		end
+
+		it "can annotate the current task that has started" do
+			task = Async::Task.new(reactor) do |task|
+				task.annotate("Hello World")
+
+				sleep
+			end
+
+			expect(task.fiber).to be_nil
+
+			task.run
+
+			expect(task.fiber.annotation).to be == "Hello World"
+		end
+	end
+
 	with '.yield' do
 		it "can yield back to scheduler" do
 			state = nil