export default function sum(arr) {
  // TODO: Return the sum of all numeric elements, ignoring non-numbers
  throw new Error('Not implemented');
}

import sum from './sum';

describe('sum', () => {
  test('sums numbers in a simple array', () => {
    expect(sum([1, 2, 3])).toBe(6);
  });

  test('ignores non-numeric values', () => {
    expect(sum(['a', 5, true, 7])).toBe(12);
  });

  test('ignores numeric strings', () => {
    expect(sum([10, '20', 30])).toBe(40);
  });

  test('returns 0 for empty or all-non-numeric arrays', () => {
    expect(sum([])).toBe(0);
    expect(sum(['x', false, null])).toBe(0);
  });
});