add .flush() test case

Author: inventshah

Lib/test/test_io/test_bufferedio.py

@@ -969,6 +969,7 @@ class MockRawIOWithoutClosed(self.MockRawIO):
 
         bufio = self.tp(MockRawIOWithoutClosed())
         self.assertRaises(TypeError, bufio.write, b"")
+        self.assertRaises(TypeError, bufio.flush)
         self.assertRaises(TypeError, bufio.close)
 
 

Modules/_io/bufferedio.c

@@ -362,7 +362,7 @@ _enter_buffered_busy(buffered *self)
     }
 
 #define IS_CLOSED(self) \
-    (!self->buffer ? !self->buffer : \
+    (!self->buffer ? 1 : \
     (self->fast_closed_checks \
      ? _PyFileIO_closed(self->raw) \
      : buffered_closed(self)))