[ruby/io-wait] Refined uncommon device type tests

https://github.com/ruby/io-wait/commit/0c73ebcf5d

test/io/wait/test_io_wait_uncommon.rb

@@ -6,15 +6,10 @@ require 'io/wait'
 # We may optimize IO#wait_*able for non-Linux kernels in the future
 class TestIOWaitUncommon < Test::Unit::TestCase
   def test_tty_wait
-    begin
-      tty = File.open('/dev/tty', 'w+')
-    rescue Errno::ENOENT, Errno::ENXIO => e
-      skip "/dev/tty: #{e.message} (#{e.class})"
+    check_dev('/dev/tty', mode: 'w+') do |tty|
+      assert_include [ nil, tty ], tty.wait_readable(0)
+      assert_equal tty, tty.wait_writable(1), 'portability test'
     end
-    assert_include [ nil, tty ], tty.wait_readable(0)
-    assert_equal tty, tty.wait_writable(1), 'portability test'
-  ensure
-    tty&.close
   end
 
   def test_fifo_wait
@@ -44,36 +39,40 @@ class TestIOWaitUncommon < Test::Unit::TestCase
 
   # used to find portability problems because some ppoll implementations
   # are incomplete and do not work for certain "file" types
-  def check_dev(dev, m = :wait_readable)
+  def check_dev(dev, m = :wait_readable, mode: m == :wait_readable ? 'r' : 'w', &block)
     begin
-      fp = File.open("/dev/#{dev}", m == :wait_readable ? 'r' : 'w')
+      fp = File.open(dev, mode)
+    rescue Errno::ENOENT
+      return # Ignore silently
     rescue SystemCallError => e
       skip "#{dev} could not be opened #{e.message} (#{e.class})"
     end
-    assert_same fp, fp.__send__(m)
+    if block
+      yield fp
+    else
+      assert_same fp, fp.__send__(m)
+    end
   ensure
     fp&.close
   end
 
   def test_wait_readable_urandom
-    check_dev 'urandom'
+    check_dev('/dev/urandom')
   end
 
   def test_wait_readable_random
-    File.open('/dev/random') do |fp|
+    check_dev('/dev/random') do |fp|
       assert_nothing_raised do
         fp.wait_readable(0)
       end
     end
-  rescue SystemCallError => e
-    skip "/dev/random could not be opened #{e.message} (#{e.class})"
   end
 
   def test_wait_readable_zero
-    check_dev 'zero'
+    check_dev('/dev/zero')
   end
 
   def test_wait_writable_null
-    check_dev 'null', :wait_writable
+    check_dev(IO::NULL, :wait_writable)
   end
 end