lodash/test/invertBy.spec.ts

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

describe('invertBy', () => {
    const object = { a: 1, b: 2, c: 1 };

    it('should transform keys by `iteratee`', () => {
        const expected = { group1: ['a', 'c'], group2: ['b'] };

        const actual = invertBy(object, (value) => `group${value}`);

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

    it('should use `_.identity` when `iteratee` is nullish', () => {
        const values = [, null, undefined],
            expected = lodashStable.map(
                values,
                lodashStable.constant({ '1': ['a', 'c'], '2': ['b'] }),
            );

        const actual = lodashStable.map(values, (value, index) =>
            index ? invertBy(object, value) : invertBy(object),
        );

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

    it('should only add multiple values to own, not inherited, properties', () => {
        const object = { a: 'hasOwnProperty', b: 'constructor' },
            expected = { hasOwnProperty: ['a'], constructor: ['b'] };

        assert.ok(lodashStable.isEqual(invertBy(object), expected));
    });

    it('should return a wrapped value when chaining', () => {
        const wrapped = _(object).invertBy();

        assert.ok(wrapped instanceof _);
        assert.deepEqual(wrapped.value(), { '1': ['a', 'c'], '2': ['b'] });
    });
});