Merge pull request #1438 from matkoniecz/feature/dummy-fetch

Add mocking of fetch so test will work again.

app/src/frontend/app.test.tsx

@@ -4,6 +4,38 @@ import { MemoryRouter } from 'react-router-dom';
 
 import { App } from './app';
 
+const originalFetch = global.fetch;
+
+beforeAll(() => {
+    global.fetch = jest.fn(() =>
+        Promise.resolve({
+            ok: true,
+            status: 200,
+            json: () =>
+                Promise.resolve({
+                    type: "FeatureCollection",
+                    features: [], // Ensure this is an array, even if empty
+                }),
+            headers: new Headers(),
+            redirected: false,
+            statusText: "OK",
+            type: "basic",
+            url: "",
+            clone: jest.fn(),
+            body: null,
+            bodyUsed: false,
+            text: jest.fn(),
+            blob: jest.fn(),
+            formData: jest.fn(),
+            arrayBuffer: jest.fn(),
+        })
+    ) as jest.Mock;
+});
+
+afterAll(() => {
+    global.fetch = originalFetch;
+});
+
 describe('<App />', () => {
     test('renders without exploding', () => {
         const div = document.createElement('div');