Test of the procedure to copy a file in java

I am trying to implement TDD and code coverage in my new projects but for one that I am developing right now I have tried to create some test cases, but I have multiple doubts respect. Here I share the class that I created to copy a file from my file system:

import java.io.File;
import java.io.IOException;
import java.text.ParseException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

import com.google.common.io.Files;

@Component
public class CopyXMLFileToResources {


    @Value("${xml.routing.folder}")
    private String XML_FOLDER;

    @Value("${resources.folder}")
    private String RESOURCES_FOLDER;

    private final Logger LOG = LoggerFactory.getLogger(CopyXMLFileToResources.class);

    @Scheduled(cron = "${cron.files.copy}", zone = "${zone.files.copy}")
    public void copyXMLFile() throws IOException {

    LOG.info("Copying the lastest varsion of  Delta file ...");

    File directory = validateDirectory(XML_FOLDER);

    if (directory.canRead()) {

        try {

        File origin = Utils.prepareDeltaFile(directory);
        if (origin != null) {
            File copied = new File(RESOURCES_FOLDER + origin.getName());
            if (copied.getTotalSpace() > 0) {
            LOG.info("Last version already copied.");
            }
            else {
                try {
                    Files.copy(origin, copied);
                    LOG.info(
                        "Copying the  DELTA file successful");
                }
                catch (Exception e) {
                    LOG.error(e.getMessage());
                }
            }

        }
        else {
            LOG.warn("No matching files fouded in {}",
                directory.getCanonicalPath());
        }

        }
        catch (ParseException e) {
        LOG.error(e.getMessage()); 
        }

    }
    else {
        LOG.warn("Cannot read folder {}. ", XML_FOLDER);
    }

    }

    private File validateDirectory (String folder) {
    return new File(folder);
    }

    public String printString(String s ) {
    return s;
    }

}

I know there are many things to improve, but my first question is, what features should be tested and where to start? Poraue I created a class Test but I do not know what to try, I tried to start by trying the access to the folder but this made me think if I need to return something as a code depending on the case, for example 0 for access denied, 1 when everything goes well for example. This class has only one public method and is of type void . I also have questions about the properties I am using:

application.properties :

xml.routing.folder=../../xml
resources.folder=src/main/resources/
cron.files.copy=0 1 1 * * *
zone.files.copy=Europe/Paris

Is it correct to do it this way? If I change the project to another server, access to the folder containing the xml can be denied. I have not created Test before so I would appreciate recommendations to get started, especially from TDD.