test_io.rb: use assert_not_predicate

* test/ruby/test_io.rb (test_DATA_binmode): assert_not_predicate
  for more descriptive message.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56432 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 3 insertions, 8 deletions

diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index e784c30c07..5c713451df 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -2470,15 +2470,10 @@ End
   end
 
   def test_DATA_binmode
-    make_tempfile {|t|
-      open(t.path, "w") {|f|
-        f.puts <<-SRC
-puts DATA.binmode?
+    assert_separately([], <<-SRC)
+assert_not_predicate(DATA, :binmode?)
 __END__
-        SRC
-      }
-      assert_in_out_err(t.path, [], %w(false))
-    }
+    SRC
   end
 
   def test_threaded_flush