test(#248): add deleteWithDescendants test coverage to TagServiceTest

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/test/java/org/raddatz/familienarchiv/service/TagServiceTest.java

@@ -375,6 +375,46 @@ class TagServiceTest {
         assertThat(result).isEqualTo(target);
     }
 
+    // ─── deleteWithDescendants ────────────────────────────────────────────────
+
+    @Test
+    void deleteWithDescendants_throwsNotFound_whenTagMissing() {
+        UUID id = UUID.randomUUID();
+        when(tagRepository.findById(id)).thenReturn(Optional.empty());
+
+        assertThatThrownBy(() -> tagService.deleteWithDescendants(id))
+                .isInstanceOf(DomainException.class)
+                .extracting(e -> ((DomainException) e).getCode())
+                .isEqualTo(ErrorCode.TAG_NOT_FOUND);
+    }
+
+    @Test
+    void deleteWithDescendants_deletesSubtreeDocTagsAndAllTags() {
+        UUID id = UUID.randomUUID();
+        UUID childId = UUID.randomUUID();
+        Tag tag = Tag.builder().id(id).name("Root").build();
+        when(tagRepository.findById(id)).thenReturn(Optional.of(tag));
+        when(tagRepository.findDescendantIds(id)).thenReturn(List.of(id, childId));
+
+        tagService.deleteWithDescendants(id);
+
+        verify(tagRepository).deleteDocumentTagsByTagIds(List.of(id, childId));
+        verify(tagRepository).deleteAllById(List.of(id, childId));
+    }
+
+    @Test
+    void deleteWithDescendants_whenLeafTag_deletesTagAndItsOwnDocTags() {
+        UUID id = UUID.randomUUID();
+        Tag tag = Tag.builder().id(id).name("Leaf").build();
+        when(tagRepository.findById(id)).thenReturn(Optional.of(tag));
+        when(tagRepository.findDescendantIds(id)).thenReturn(List.of(id));
+
+        tagService.deleteWithDescendants(id);
+
+        verify(tagRepository).deleteDocumentTagsByTagIds(List.of(id));
+        verify(tagRepository).deleteAllById(List.of(id));
+    }
+
     // ─── delete ───────────────────────────────────────────────────────────────
 
     @Test