test: remove test-util (#1266)

src/components/AllRead.test.tsx

@@ -1,11 +1,18 @@
 import { render } from '@testing-library/react';
 import { AllRead } from './AllRead';
-import { mockMathRandom } from './test-utils';
 
 describe('components/AllRead.tsx', () => {
+  const originalMathRandom = Math.random;
+
   // The read emoji randomly rotates, but then the snapshots would never match
   // Have to make it consistent so the emojis are always the same
-  mockMathRandom(0.1);
+  beforeEach(() => {
+    global.Math.random = jest.fn(() => 0.1);
+  });
+
+  afterEach(() => {
+    global.Math.random = originalMathRandom;
+  });
 
   it('should render itself & its children', () => {
     const tree = render(<AllRead />);