export default function arrayForEach(arr, callbackFn, thisArg) {
  // Requirements:
  // - Snapshot initial length (do not visit appended elements beyond initial length)
  // - Skip holes (sparse slots)
  // - Skip elements deleted before their index is reached
  // - Bind thisArg using .call
  throw new Error('Not implemented');
}

import arrayForEach from './file';

describe('arrayForEach', () => {
  test('iterates in order', () => {
    const seen = [];
    arrayForEach([3, 1, 2], (v) => seen.push(v));
    expect(seen).toEqual([3, 1, 2]);
  });

  test('binds thisArg', () => {
    const ctx = { out: '' };
    arrayForEach(['a', 'b'], function (v) { this.out += v; }, ctx);
    expect(ctx.out).toBe('ab');
  });

  test('skips holes (sparse arrays)', () => {
    // eslint-disable-next-line no-sparse-arrays
    const a = [1, , 3];
    const seen = [];
    arrayForEach(a, (v, i) => seen.push([v, i]));
    expect(seen).toEqual([[1, 0], [3, 2]]);
  });

  test('snapshots length (push during iteration not visited)', () => {
    const arr = [1, 2, 3];
    const seen = [];

    arrayForEach(arr, (v, i, a) => {
      seen.push(v);
      if (i === 0) a.push(999);
    });

    expect(seen).toEqual([1, 2, 3]);
  });

  test('skips elements deleted before their turn (hole check)', () => {
    const arr = [1, 2, 3];
    const seen = [];

    arrayForEach(arr, (v, i, a) => {
      if (i === 0) delete a[1];
      seen.push(v);
    });

    // index 1 was deleted before iteration reached it => skip it
    expect(seen).toEqual([1, 3]);
  });
});