updated test to check for proper formatter prop value

__tests__/formatter-value-tests.js

@@ -0,0 +1,26 @@
+import '@testing-library/jest-dom'
+import { render, screen } from '@testing-library/react'
+import React from 'react'
+import TimeAgo from '../src'
+
+it('should handle null formatter gracefully', () => {
+  render(<TimeAgo date={Date.now() - 1000 * 60} formatter={null} />)
+  expect(screen.getByText('1 minute ago')).toBeInTheDocument()
+})
+
+it('should handle empty function formatter', () => {
+  render(<TimeAgo date={Date.now() - 2000 * 60 * 60} formatter={() => {}} />)
+  expect(screen.getByText('2 hours ago')).toBeInTheDocument()
+})
+
+it('should handle formatter throwing an error', () => {
+  render(
+    <TimeAgo
+      date={Date.now() - 2000 * 60}
+      formatter={() => {
+        throw new Error('Faulty formatter')
+      }}
+    />,
+  )
+  expect(screen.getByText('2 minutes ago')).toBeInTheDocument()
+})