test(frontend): add unit tests for FileSaverService

frontend/src/app/dashboard/service/user/file/file-saver.service.spec.ts

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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { TestBed } from "@angular/core/testing";
+import { saveAs } from "file-saver";
+import { FileSaverService } from "./file-saver.service";
+
+// Replace the file-saver module wholesale (same precedent as menu.component.spec.ts);
+// the service is a thin passthrough, so we assert it forwards to saveAs unchanged.
+vi.mock("file-saver", () => ({ saveAs: vi.fn() }));
+
+describe("FileSaverService", () => {
+  let service: FileSaverService;
+
+  beforeEach(() => {
+    vi.mocked(saveAs).mockClear();
+    TestBed.configureTestingModule({ providers: [FileSaverService] });
+    service = TestBed.inject(FileSaverService);
+  });
+
+  it("should be created", () => {
+    expect(service).toBeTruthy();
+  });
+
+  it("delegates a Blob payload to saveAs with filename and options", () => {
+    const blob = new Blob(["hello"], { type: "text/plain" });
+    const options = { autoBom: true };
+
+    service.saveAs(blob, "greeting.txt", options);
+
+    expect(saveAs).toHaveBeenCalledTimes(1);
+    expect(saveAs).toHaveBeenCalledWith(blob, "greeting.txt", options);
+  });
+
+  it("forwards a string payload (e.g. a URL) unchanged", () => {
+    service.saveAs("https://example.com/file.csv", "file.csv");
+
+    expect(saveAs).toHaveBeenCalledWith("https://example.com/file.csv", "file.csv", undefined);
+  });
+
+  it("passes undefined through when filename and options are omitted", () => {
+    const blob = new Blob([]);
+
+    service.saveAs(blob);
+
+    expect(saveAs).toHaveBeenCalledWith(blob, undefined, undefined);
+  });
+});