diff --git a/src/main/java/org/jabref/logic/exporter/XmpExporter.java b/src/main/java/org/jabref/logic/exporter/XmpExporter.java
index 9a045f8ebc8..59f7c445b6b 100644
--- a/src/main/java/org/jabref/logic/exporter/XmpExporter.java
+++ b/src/main/java/org/jabref/logic/exporter/XmpExporter.java
@@ -24,7 +24,7 @@
  */
 public class XmpExporter extends Exporter {
 
-    private static final String XMP_SPLIT_PATTERN = "split";
+    public static final String XMP_SPLIT_DIRECTORY_INDICATOR = "split";
 
     private final XmpPreferences xmpPreferences;
 
@@ -33,6 +33,12 @@ public XmpExporter(XmpPreferences xmpPreferences) {
         this.xmpPreferences = xmpPreferences;
     }
 
+    /**
+     * @param databaseContext the database to export from
+     * @param file            the file to write to. If it contains "split", then the output is split into different files
+     * @param encoding        the encoding to use
+     * @param entries         a list containing all entries that should be exported
+     */
     @Override
     public void export(BibDatabaseContext databaseContext, Path file, Charset encoding, List<BibEntry> entries) throws Exception {
         Objects.requireNonNull(databaseContext);
@@ -45,18 +51,16 @@ public void export(BibDatabaseContext databaseContext, Path file, Charset encodi
 
         // This is a distinction between writing all entries from the supplied list to a single .xmp file,
         // or write every entry to a separate file.
-        if (file.getFileName().toString().trim().equals(XMP_SPLIT_PATTERN)) {
-
+        if (file.getFileName().toString().trim().equals(XMP_SPLIT_DIRECTORY_INDICATOR)) {
             for (BibEntry entry : entries) {
                 // Avoid situations, where two cite keys are null
                 Path entryFile;
-                String suffix = entry.getId() + "_" + entry.getField(InternalField.KEY_FIELD).orElse("") + ".xmp";
+                String suffix = entry.getId() + "_" + entry.getField(InternalField.KEY_FIELD).orElse("null") + ".xmp";
                 if (file.getParent() == null) {
                     entryFile = Paths.get(suffix);
                 } else {
                     entryFile = Paths.get(file.getParent().toString() + "/" + suffix);
                 }
-
                 this.writeBibToXmp(entryFile, Collections.singletonList(entry), encoding);
             }
         } else {
@@ -66,7 +70,6 @@ public void export(BibDatabaseContext databaseContext, Path file, Charset encodi
 
     private void writeBibToXmp(Path file, List<BibEntry> entries, Charset encoding) throws IOException {
         String xmpContent = XmpUtilWriter.generateXmpStringWithoutXmpDeclaration(entries, this.xmpPreferences);
-
         try (BufferedWriter writer = Files.newBufferedWriter(file, encoding)) {
             writer.write(xmpContent);
             writer.flush();
diff --git a/src/test/java/org/jabref/logic/exporter/XmpExporterTest.java b/src/test/java/org/jabref/logic/exporter/XmpExporterTest.java
index d102c01aa39..120d27f8638 100644
--- a/src/test/java/org/jabref/logic/exporter/XmpExporterTest.java
+++ b/src/test/java/org/jabref/logic/exporter/XmpExporterTest.java
@@ -119,22 +119,23 @@ public void writeMultipleEntriesInASingleFile(@TempDir Path testFolder) throws E
 
     @Test
     public void writeMultipleEntriesInDifferentFiles(@TempDir Path testFolder) throws Exception {
-        Path file = testFolder.resolve("split");
+        // set path to the one where the exporter produces several files
+        Path file = testFolder.resolve(XmpExporter.XMP_SPLIT_DIRECTORY_INDICATOR);
         Files.createFile(file);
 
-        BibEntry entryTuring = new BibEntry();
-        entryTuring.setField(StandardField.AUTHOR, "Alan Turing");
+        BibEntry entryTuring = new BibEntry()
+                .withField(StandardField.AUTHOR, "Alan Turing");
 
-        BibEntry entryArmbrust = new BibEntry();
-        entryArmbrust.setField(StandardField.AUTHOR, "Michael Armbrust");
-        entryArmbrust.setCiteKey("Armbrust2010");
+        BibEntry entryArmbrust = new BibEntry()
+                .withField(StandardField.AUTHOR, "Michael Armbrust")
+                .withCiteKey("Armbrust2010");
 
-        exporter.export(databaseContext, file, encoding, Arrays.asList(entryTuring, entryArmbrust));
+        exporter.export(databaseContext, file, encoding, List.of(entryTuring, entryArmbrust));
 
         List<String> lines = Files.readAllLines(file);
         assertEquals(Collections.emptyList(), lines);
 
-        Path fileTuring = Paths.get(file.getParent().toString() + "/" + entryTuring.getId() + "_null.xmp");
+        Path fileTuring = Paths.get(file.getParent().toString(), entryTuring.getId() + "_null.xmp");
         String actualTuring = String.join("\n", Files.readAllLines(fileTuring)); // we are using \n to join, so we need it in the expected string as well, \r\n would fail
 
         String expectedTuring = "  <rdf:RDF xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\">\n" +
@@ -155,7 +156,7 @@ public void writeMultipleEntriesInDifferentFiles(@TempDir Path testFolder) throw
 
         assertEquals(expectedTuring, actualTuring);
 
-        Path fileArmbrust = Paths.get(file.getParent().toString() + "/" + entryArmbrust.getId() + "_Armbrust2010.xmp");
+        Path fileArmbrust = Paths.get(file.getParent().toString(), entryArmbrust.getId() + "_Armbrust2010.xmp");
         String actualArmbrust = String.join("\n", Files.readAllLines(fileArmbrust)); // we are using \n to join, so we need it in the expected string as well, \r\n would fail
 
         String expectedArmbrust = "  <rdf:RDF xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\">\n" +