test(DatenDeleteAttachmentTest): NullPointerException in setUp

src/main/java/de/danielluedecke/zettelkasten/database/Daten.java

@@ -4564,7 +4564,7 @@ public void setAttachments(int pos, String[] attachments) {
 	 *
 	 * @param pos         the entry from which we want to set/change the hyperlinks
 	 *                    and attachments
-	 * @param attachments a string-array containing the hyperlinks, attachmentspaths
+	 * @param attachments a string-array containing the hyperlinks, attachments paths
 	 *                    etc.
 	 */
 	public void addAttachments(int pos, String[] attachments) {
@@ -4574,10 +4574,10 @@ public void addAttachments(int pos, String[] attachments) {
 		if (null == entry || null == attachments || attachments.length < 1) {
 			return;
 		}
-		// save modification-stata
+		// save modification-state
 		boolean mod = false;
 		// add each hyperlink string
-		// therefor, iterate the array
+		// therefore, iterate the array
 		for (String a : attachments) {
 			try {
 				// create a new subchuld-element

src/test/java/de/danielluedecke/zettelkasten/database/DatenDeleteAttachmentTest.java

@@ -0,0 +1,59 @@
+package de.danielluedecke.zettelkasten.database;
+
+import de.danielluedecke.zettelkasten.ZettelkastenView;
+import de.danielluedecke.zettelkasten.settings.Settings;
+import org.jdom2.Element;
+import org.testng.Assert;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+import org.mockito.Mockito;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class DatenDeleteAttachmentTest {
+    private Daten daten;
+    private int entryNumber;
+
+    @BeforeMethod
+    public void setUp() {
+        // Mock the required dependencies
+        ZettelkastenView view = Mockito.mock(ZettelkastenView.class);
+        Settings settings = Mockito.mock(Settings.class);
+        Synonyms synonyms = Mockito.mock(Synonyms.class);
+        BibTeX bibTeX = Mockito.mock(BibTeX.class);
+
+        // Initialize Daten with mocks
+        daten = new Daten(view, settings, synonyms, bibTeX);
+        entryNumber = 1;
+
+        // Set up multiple duplicate attachments using addAttachments
+        String[] attachments = {"attachment1.pdf", "attachment1.pdf", "attachment1.pdf"};
+        daten.addAttachments(entryNumber, attachments);
+
+        // Confirm attachments are added
+        List<Element> initialAttachments = daten.getAttachments(entryNumber);
+        Assert.assertEquals(initialAttachments.size(), 3, "Three instances of the attachment should have been added.");
+    }
+
+    @Test
+    public void testDeleteAttachmentListedMultipleTimes() {
+        // Attempt to delete an attachment that is listed three times
+        daten.deleteAttachment("attachment1.pdf", entryNumber);
+
+        // Get remaining attachments as Elements
+        List<Element> remainingElements = daten.getAttachments(entryNumber);
+
+        // Extract text values from Element objects for assertion
+        List<String> remainingAttachments = remainingElements == null
+                ? Collections.emptyList()
+                : remainingElements.stream()
+                .map(Element::getText)
+                .collect(Collectors.toList());
+
+        // Assert that all instances are deleted
+        Assert.assertTrue(remainingAttachments.isEmpty(),
+                "All instances of the attachment should be deleted, but duplicates may remain.");
+    }
+}