def test_capabilities(): sio = StringIO() assert sio.readable() assert sio.writable() assert sio.seekable() assert not sio.isatty() assert not sio.closed assert not sio.line_buffering sio.close() raises(ValueError, sio.readable) raises(ValueError, sio.writable) raises(ValueError, sio.seekable) raises(ValueError, sio.isatty) assert sio.closed assert sio.errors is None