Mocking calender Build function which take input stream

@mock
private MultipartFile multipart;
public int filexyz(Map map,MulitpartFile file){
InputStream in = file.getInputStream();
CalenderBuilder builder = new CalenderBuilder();
calender = builder.build(in);///this  line causing parsing error
}
@Test
public void filexyzTest(){
InputStream in  = new ByteArrayInputStream("2000,1,MONDAY\\n".getBytes(StandardCharsets.UTF_8));
when(multipart.getInputStream().thenReturn(in);
xyz.filexyz(map,multipartFile);

} I am testing the function but it thrwoing error,parsingException any helpenter code here