lodash/test/concat.spec.ts

import assert from 'node:assert';
import lodashStable from 'lodash';
import concat from '../src/concat';

describe('concat', () => {
    it('should shallow clone `array`', () => {
        const array = [1, 2, 3],
            actual = concat(array);

        assert.deepStrictEqual(actual, array);
        assert.notStrictEqual(actual, array);
    });

    it('should concat arrays and values', () => {
        const array = [1],
            actual = concat(array, 2, [3], [[4]]);

        assert.deepStrictEqual(actual, [1, 2, 3, [4]]);
        assert.deepStrictEqual(array, [1]);
    });

    it('should cast non-array `array` values to arrays', () => {
        const values = [, null, undefined, false, true, 1, NaN, 'a'];

        let expected = lodashStable.map(values, (value, index) => (index ? [value] : []));

        let actual = lodashStable.map(values, (value, index) => (index ? concat(value) : concat()));

        assert.deepStrictEqual(actual, expected);

        expected = lodashStable.map(values, (value) => [value, 2, [3]]);

        actual = lodashStable.map(values, (value) => concat(value, [2], [[3]]));

        assert.deepStrictEqual(actual, expected);
    });

    it('should treat sparse arrays as dense', () => {
        const expected = [],
            actual = concat(Array(1), Array(1));

        expected.push(undefined, undefined);

        assert.ok('0' in actual);
        assert.ok('1' in actual);
        assert.deepStrictEqual(actual, expected);
    });

    it('should return a new wrapped array', () => {
        const array = [1],
            wrapped = _(array).concat([2, 3]),
            actual = wrapped.value();

        assert.deepEqual(array, [1]);
        assert.deepEqual(actual, [1, 2, 3]);
    });
});