Improve line covearge of ext/io/nonblock/nonblock.c from 54.5% to 95.5%

Not so good test, but it would be better than nothing, I guess...

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59741 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/io/nonblock/nonblock.c

@@ -1,6 +1,6 @@
 /**********************************************************************
 
-  io/wait.c -
+  io/nonblock.c -
 
   $Author$
   created at: Tue Jul 14 21:53:18 2009

test/io/nonblock/test_flush.rb

@@ -50,4 +50,22 @@ class TestIONonblock < Test::Unit::TestCase
     assert_equal(4097, result.size)
     true
   end
+
+  def test_nonblock
+    IO.pipe {|r, w|
+      assert_equal(false, w.nonblock?)
+      w.nonblock do
+        assert_equal(true, w.nonblock?)
+        w.nonblock(false) do
+          assert_equal(false, w.nonblock?)
+          w.nonblock(false) do
+            assert_equal(false, w.nonblock?)
+          end
+          assert_equal(false, w.nonblock?)
+        end
+        assert_equal(true, w.nonblock?)
+      end
+      assert_equal(false, w.nonblock?)
+    }
+  end
 end if IO.method_defined?(:nonblock)