diff --git a/web/src/app/administration/services/classification-tree.service.spec.ts b/web/src/app/administration/services/classification-tree.service.spec.ts
new file mode 100644
index 000000000..d57c13845
--- /dev/null
+++ b/web/src/app/administration/services/classification-tree.service.spec.ts
@@ -0,0 +1,53 @@
+import { ClassificationTreeService } from './classification-tree.service';
+import { TestBed } from '@angular/core/testing';
+import { Classification } from '../../shared/models/classification';
+import { TreeNodeModel } from '../models/tree-node';
+
+describe('ClassificationTreeService', () => {
+  let service: ClassificationTreeService;
+
+  beforeEach(() => {
+    TestBed.configureTestingModule({ providers: [ClassificationTreeService] });
+    service = TestBed.inject(ClassificationTreeService);
+  });
+
+  it('transformToTreeNodes() should return treeNodeModel list sorted by key with empty children', () => {
+    const classifications: Classification[] = [
+      { classificationId: 'ID21', key: 'KEY1' },
+      { classificationId: 'ID13', key: 'KEY3' },
+      { classificationId: 'ID42', key: 'KEY2' }
+    ];
+    const expectedTreeNodes: TreeNodeModel[] = [
+      { classificationId: 'ID21', key: 'KEY1', children: [] },
+      { classificationId: 'ID42', key: 'KEY2', children: [] },
+      { classificationId: 'ID13', key: 'KEY3', children: [] }
+    ];
+    expect(service.transformToTreeNode(classifications)).toStrictEqual(expectedTreeNodes);
+  });
+
+  it('transformToTreeNodes() should return treeNodeModel list sorted by key with children', () => {
+    const classifications: Classification[] = [
+      { classificationId: 'ID4', key: 'KEY4' },
+      { classificationId: 'ID1', key: 'KEY1' },
+      { classificationId: 'ID3', key: 'KEY3', parentId: 'ID1', parentKey: 'KEY1' },
+      { classificationId: 'ID2', key: 'KEY2', parentId: 'ID3', parentKey: 'KEY3' }
+    ];
+    const expectedTreeNodes: TreeNodeModel[] = [
+      {
+        classificationId: 'ID1',
+        key: 'KEY1',
+        children: [
+          {
+            classificationId: 'ID3',
+            key: 'KEY3',
+            parentId: 'ID1',
+            parentKey: 'KEY1',
+            children: [{ classificationId: 'ID2', key: 'KEY2', parentId: 'ID3', parentKey: 'KEY3', children: [] }]
+          }
+        ]
+      },
+      { classificationId: 'ID4', key: 'KEY4', children: [] }
+    ];
+    expect(service.transformToTreeNode(classifications)).toStrictEqual(expectedTreeNodes);
+  });
+});