core-js/tests/unit-global/es.array.fill.js

import { DESCRIPTORS, NATIVE, STRICT } from '../helpers/constants.js';

QUnit.test('Array#fill', assert => {
  const { fill } = Array.prototype;
  assert.isFunction(fill);
  assert.arity(fill, 1);
  assert.name(fill, 'fill');
  assert.looksNative(fill);
  assert.nonEnumerable(Array.prototype, 'fill');
  const array = new Array(5);
  assert.same(array.fill(5), array);
  assert.deepEqual(Array(5).fill(5), [5, 5, 5, 5, 5]);
  assert.deepEqual(Array(5).fill(5, 1), [undefined, 5, 5, 5, 5]);
  assert.deepEqual(Array(5).fill(5, 1, 4), [undefined, 5, 5, 5, undefined]);
  assert.deepEqual(Array(5).fill(5, 6, 1), [undefined, undefined, undefined, undefined, undefined]);
  assert.deepEqual(Array(5).fill(5, -3, 4), [undefined, undefined, 5, 5, undefined]);
  assert.arrayEqual(fill.call({ length: 5 }, 5), [5, 5, 5, 5, 5]);
  if (STRICT) {
    assert.throws(() => fill.call(null, 0), TypeError);
    assert.throws(() => fill.call(undefined, 0), TypeError);
  }
  if (NATIVE && DESCRIPTORS) {
    assert.notThrows(() => fill.call(Object.defineProperty({
      length: -1,
    }, 0, {
      set() {
        throw new Error();
      },
    })), 'uses ToLength');
  }
  assert.true('fill' in Array.prototype[Symbol.unscopables], 'In Array#@@unscopables');
});