/**
* Tests for utils/imageUtils.ts
*
* Covers:
* - fetchImageAsBase64: success, charset stripping, MIME inference, error cases
* - imageContentBlock: correct shape
*/
import { jest } from '@jest/globals';
// Mock axios before importing the module under test
const mockAxiosGet = jest.fn<(...args: any[]) => Promise<any>>();
jest.unstable_mockModule('axios', () => ({
default: { get: mockAxiosGet },
}));
const { fetchImageAsBase64, imageContentBlock } = await import('../../utils/imageUtils.js');
beforeEach(() => {
jest.clearAllMocks();
});
// ── fetchImageAsBase64 ───────────────────────────────────────────────────────
describe('fetchImageAsBase64', () => {
function makeAxiosResponse(data: ArrayBuffer, contentType?: string) {
const headers: Record<string, string> = {};
if (contentType !== undefined) {
headers['content-type'] = contentType;
}
return { data, headers };
}
test('success: returns base64 data and mimeType from Content-Type header', async () => {
const bytes = new Uint8Array([0x89, 0x50, 0x4e, 0x47]); // PNG magic
mockAxiosGet.mockResolvedValueOnce(
makeAxiosResponse(bytes.buffer, 'image/png')
);
const result = await fetchImageAsBase64('https://example.com/img.png');
expect(result).not.toBeNull();
expect(result!.mimeType).toBe('image/png');
expect(typeof result!.data).toBe('string');
// Verify base64 round-trip
const decoded = Buffer.from(result!.data, 'base64');
expect(decoded[0]).toBe(0x89);
});
test('strips charset from Content-Type', async () => {
const bytes = new Uint8Array([0xff, 0xd8]);
mockAxiosGet.mockResolvedValueOnce(
makeAxiosResponse(bytes.buffer, 'image/jpeg; charset=utf-8')
);
const result = await fetchImageAsBase64('https://example.com/photo.jpg');
expect(result).not.toBeNull();
expect(result!.mimeType).toBe('image/jpeg');
});
test('infers MIME from URL extension when no Content-Type header', async () => {
const bytes = new Uint8Array([0x47, 0x49, 0x46]); // GIF magic
mockAxiosGet.mockResolvedValueOnce(
makeAxiosResponse(bytes.buffer, undefined)
);
const result = await fetchImageAsBase64('https://example.com/anim.gif');
expect(result).not.toBeNull();
expect(result!.mimeType).toBe('image/gif');
});
test('infers image/jpeg for .jpg extension', async () => {
const bytes = new Uint8Array([1]);
mockAxiosGet.mockResolvedValueOnce(makeAxiosResponse(bytes.buffer, ''));
const result = await fetchImageAsBase64('https://example.com/photo.jpg');
expect(result!.mimeType).toBe('image/jpeg');
});
test('infers image/jpeg for .jpeg extension', async () => {
const bytes = new Uint8Array([1]);
mockAxiosGet.mockResolvedValueOnce(makeAxiosResponse(bytes.buffer, ''));
const result = await fetchImageAsBase64('https://example.com/photo.jpeg');
expect(result!.mimeType).toBe('image/jpeg');
});
test('infers image/webp for .webp extension', async () => {
const bytes = new Uint8Array([1]);
mockAxiosGet.mockResolvedValueOnce(makeAxiosResponse(bytes.buffer, ''));
const result = await fetchImageAsBase64('https://example.com/photo.webp');
expect(result!.mimeType).toBe('image/webp');
});
test('falls back to image/png for unknown extension', async () => {
const bytes = new Uint8Array([1]);
mockAxiosGet.mockResolvedValueOnce(makeAxiosResponse(bytes.buffer, ''));
const result = await fetchImageAsBase64('https://example.com/image.bmp');
expect(result!.mimeType).toBe('image/png');
});
test('returns null when axios throws (network error)', async () => {
mockAxiosGet.mockRejectedValueOnce(new Error('Network Error'));
const result = await fetchImageAsBase64('https://example.com/img.png');
expect(result).toBeNull();
});
test('returns null when axios throws (404-like error)', async () => {
const err = Object.assign(new Error('Request failed'), {
response: { status: 404 },
});
mockAxiosGet.mockRejectedValueOnce(err);
const result = await fetchImageAsBase64('https://example.com/missing.png');
expect(result).toBeNull();
});
test('strips query params when inferring MIME from URL', async () => {
const bytes = new Uint8Array([1]);
mockAxiosGet.mockResolvedValueOnce(makeAxiosResponse(bytes.buffer, ''));
const result = await fetchImageAsBase64('https://example.com/photo.gif?w=100&h=100');
expect(result!.mimeType).toBe('image/gif');
});
});
// ── imageContentBlock ────────────────────────────────────────────────────────
describe('imageContentBlock', () => {
test('returns correct MCP image content block shape', () => {
const block = imageContentBlock('base64data', 'image/png');
expect(block).toEqual({
type: 'image',
data: 'base64data',
mimeType: 'image/png',
});
});
test('type is the literal string "image"', () => {
const block = imageContentBlock('x', 'image/jpeg');
expect(block.type).toBe('image');
});
});
