diff --git a/src/testdir/test87.in b/src/testdir/test87.in
index e24df41..fedc795 100644
--- a/src/testdir/test87.in
+++ b/src/testdir/test87.in
@@ -1071,8 +1071,20 @@
 ee('del sys.stdout.softspace')
 number_test('sys.stdout.softspace = %s', unsigned=True)
 number_test('sys.stderr.softspace = %s', unsigned=True)
+ee('assert sys.stdout.isatty()==False')
+ee('assert sys.stdout.seekable()==False')
+ee('sys.stdout.close()')
+ee('sys.stdout.flush()')
+ee('assert sys.stderr.isatty()==False')
+ee('assert sys.stderr.seekable()==False')
+ee('sys.stderr.close()')
+ee('sys.stderr.flush()')
 ee('sys.stdout.attr = None')
 cb.append(">> OutputWrite")
+ee('assert sys.stdout.writable()==True')
+ee('assert sys.stdout.readable()==False')
+ee('assert sys.stderr.writable()==True')
+ee('assert sys.stderr.readable()==False')
 ee('sys.stdout.write(None)')
 cb.append(">> OutputWriteLines")
 ee('sys.stdout.writelines(None)')