lodash/test/math-operator-methods.spec.ts

import assert from 'node:assert';
import lodashStable from 'lodash';
import { _, symbol } from './utils';

describe('math operator methods', () => {
    lodashStable.each(['add', 'divide', 'multiply', 'subtract'], (methodName) => {
        const func = _[methodName],
            isAddSub = methodName === 'add' || methodName === 'subtract';

        it(`\`_.${methodName}\` should return \`${
            isAddSub ? 0 : 1
        }\` when no arguments are given`, () => {
            assert.strictEqual(func(), isAddSub ? 0 : 1);
        });

        it(`\`_.${methodName}\` should work with only one defined argument`, () => {
            assert.strictEqual(func(6), 6);
            assert.strictEqual(func(6, undefined), 6);
            assert.strictEqual(func(undefined, 4), 4);
        });

        it(`\`_.${methodName}\` should preserve the sign of \`0\``, () => {
            const values = [0, '0', -0, '-0'],
                expected = [
                    [0, Infinity],
                    ['0', Infinity],
                    [-0, -Infinity],
                    ['-0', -Infinity],
                ];

            lodashStable.times(2, (index) => {
                const actual = lodashStable.map(values, (value) => {
                    const result = index ? func(undefined, value) : func(value);
                    return [result, 1 / result];
                });

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

        it(`\`_.${methodName}\` should convert objects to \`NaN\``, () => {
            assert.deepStrictEqual(func(0, {}), NaN);
            assert.deepStrictEqual(func({}, 0), NaN);
        });

        it(`\`_.${methodName}\` should convert symbols to \`NaN\``, () => {
            if (Symbol) {
                assert.deepStrictEqual(func(0, symbol), NaN);
                assert.deepStrictEqual(func(symbol, 0), NaN);
            }
        });

        it(`\`_.${methodName}\` should return an unwrapped value when implicitly chaining`, () => {
            const actual = _(1)[methodName](2);
            assert.notOk(actual instanceof _);
        });

        it(`\`_.${methodName}\` should return a wrapped value when explicitly chaining`, () => {
            const actual = _(1).chain()[methodName](2);
            assert.ok(actual instanceof _);
        });
    });
});