Verifying Currency Formatter Utility with Unit Tests

import { describe, it, expect } from 'vitest';
 
export function formatCurrency(amount, currencySymbol = '€') {
  if (typeof amount !== 'number' || Number.isNaN(amount)) {
    return '0.00 ' + currencySymbol;
  }
  return `${amount.toFixed(2)} ${currencySymbol}`;
}
 
describe('formatCurrency', () => {
  it('formats positive numbers with default currency', () => {
    const result = formatCurrency(19.99);
    expect(result).toBe('19.99 €');
  });
 
  it('handles invalid non-number input fallback', () => {
    const result = formatCurrency('invalid');
    expect(result).toBe('0.00 €');
  });
});