Unit test for uploading file on Minio Storage in Spring boot

Question

I have a service class which uses Minio Cloud storage to upload a file. I want to write a unit test for that class using Mockito. How can I do that in spring boot. Searched over internet but not able to find how will this be done. Below is my service class.

public String uploadAttachment( MultipartFile multipartFile) throws Exception{

   

    MinioClient minioClient = minioConfig.generateMinioClient();
    String fileExtension = FilenameUtils.getExtension(multipartFile.getOriginalFilename());
    String fileUrl;
    String fileName = null;
    File file = null;
    try {
        file = convertMultiPartToFile(multipartFile);
        fileName = "test";
        minioClient.putObject(bucketName, fileName, new FileInputStream(file),
                new PutObjectOptions(file.length(), -1));
        fileUrl = minioClient.getPresignedObjectUrl(Method.GET, bucketName, fileName,
                2,null);
    } catch(Exception exception) {
        
    }finally{
        file.delete();
        logger.debug("file deletion successful");
    }

    return fileUrl;

}