Don't depend on TTY ioctls for testing

spec/ruby/core/io/ioctl_spec.rb

@@ -8,23 +8,20 @@
 
   platform_is :os => :linux do
     it "replaces a String's content with the output buffer" do
-      File.open('/dev/tty', 'r') do |f|
-        # Process group ID and session ID.
-        # Ruby has Process.getpgrp but no method to get the session ID.
-        ids = `ps -j --no-heading -p #{Process.pid}`.split[1, 2].map(&:to_i)
+      File.open(__FILE__, 'r') do |f|
         buffer = ''
-        # TIOCGPGRP in /usr/include/asm-generic/ioctls.h
-        f.ioctl 0x540F, buffer
-        ids.should include(buffer.unpack('I').first)
+        # FIONREAD in /usr/include/asm-generic/ioctls.h
+        f.ioctl 0x541B, buffer
+        buffer.unpack('I').first.should be_kind_of(Integer)
       end
     end
 
     it "raises an Errno error when ioctl fails" do
-      File.open('/dev/tty', 'r') do |f|
+      File.open(__FILE__, 'r') do |f|
         lambda {
-          # TIOCGPGRP in /usr/include/asm-generic/ioctls.h
-          f.ioctl 0x540F, nil
-        }.should raise_error(Errno::EFAULT)
+          # TIOCGWINSZ in /usr/include/asm-generic/ioctls.h
+          f.ioctl 0x5413, nil
+        }.should raise_error(Errno::ENOTTY)
       end
     end
   end