Add fifo tests.

test/io/event/selector/fifo_io.rb

@@ -0,0 +1,73 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2021-2023, by Samuel Williams.
+
+require "io/event"
+require "io/event/selector"
+require "fileutils"
+require "tmpdir"
+
+FifoIO = Sus::Shared("fifo io") do
+	with "a fifo" do
+		def around(&block)
+			@root = Dir.mktmpdir
+			super
+		ensure
+			FileUtils.rm_rf(@root) if @root
+		end
+
+		let(:path) {File.join(@root, "fifo")}
+
+		it "can read and write" do
+			skip_if_ruby_platform(/mswin|mingw|cygwin/)
+
+			File.mkfifo(path)
+
+			output = File.open(path, "w+")
+			input = File.open(path, "r+")
+
+			buffer = IO::Buffer.new(128)
+
+			reader = Fiber.new do
+				@selector.io_wait(Fiber.current, input, IO::READABLE)
+				result = buffer.read(input, 0)
+				buffer.resize(result)
+			end
+
+			writer = Fiber.new do
+				output.puts("Hello World\n")
+				output.close
+			end
+
+			reader.transfer
+			writer.transfer
+
+			2.times do
+				@selector.select(0)
+			end
+
+			expect(buffer.get_string).to be == "Hello World\n"
+		end
+	end
+end
+
+IO::Event::Selector.constants.each do |name|
+	klass = IO::Event::Selector.const_get(name)
+
+	describe(klass, unique: name) do
+		def before
+			@loop = Fiber.current
+			@selector = subject.new(@loop)
+		end
+
+		def after(error = nil)
+			@selector&.close
+		end
+
+		attr :loop
+		attr :selector
+
+		it_behaves_like FifoIO
+	end
+end