downloadFromURL

1/**
2 * Downloads a file from the given URL and saves it with the specified filename.
3 *
4 * @param url - The URL to download the file from.
5 * @param filename - The desired name of the downloaded file.
6 */
7export async function downloadFromURL(url: string, filename: string): Promise<void> {
8  const response = await fetch(url);
9  if (!response.ok) {
10    throw new Error(`Failed to fetch file from ${url}`);
11  }
12
13  const blob = await response.blob();
14  const blobUrl = URL.createObjectURL(blob);
15
16  const link = document.createElement('a');
17  link.href = blobUrl;
18  link.download = filename;
19  document.body.appendChild(link);
20  link.click();
21  document.body.removeChild(link);
22  URL.revokeObjectURL(blobUrl);
23}

1beforeEach(() => {
2  global.fetch = jest.fn();
3  URL.createObjectURL = jest.fn(() => 'blob:fake-url');
4  URL.revokeObjectURL = jest.fn();
5  document.body.appendChild = jest.fn();
6  document.body.removeChild = jest.fn();
7});
8
9test('downloadFromURL - successful download triggers link click', async () => {
10  const mockClick = jest.fn();
11  const mockBlob = new Blob(['test']);
12
13  (fetch as jest.Mock).mockResolvedValue({
14    ok: true,
15    blob: () => Promise.resolve(mockBlob),
16  });
17
18  const link = { click: mockClick } as unknown as HTMLAnchorElement;
19  document.createElement = jest.fn(() => link);
20
21  await downloadFromURL('https://example.com/file.txt', 'file.txt');
22
23  expect(fetch).toHaveBeenCalledWith('https://example.com/file.txt');
24  expect(URL.createObjectURL).toHaveBeenCalledWith(mockBlob);
25  expect(mockClick).toHaveBeenCalled();
26  expect(document.body.appendChild).toHaveBeenCalledWith(link);
27  expect(document.body.removeChild).toHaveBeenCalledWith(link);
28  expect(URL.revokeObjectURL).toHaveBeenCalledWith('blob:fake-url');
29});
30
31test('downloadFromURL - throws error if fetch fails', async () => {
32  (fetch as jest.Mock).mockResolvedValue({ ok: false });
33
34  await expect(downloadFromURL('https://example.com/bad', 'bad.txt')).rejects.toThrow(
35    'Failed to fetch file from https://example.com/bad'
36  );
37});