enhancedmath/lib/__tests__/permutation.test.js

This package contains some enhanced mathematical operations

import { describe, test, expect } from 'vitest';
import permutation from '../Probability/permutation';
describe('Combination', () => {
    test('should return 1 for a 1P1', () => {
        const result = permutation(1, 1);
        expect(result).toEqual(1n);
    });
    test('should return 6 for a 4P2', () => {
        const result = permutation(4, 2);
        expect(result).toBe(12n);
    });
    test('should return 154440 for a 13P5', () => {
        const result = permutation(13, 5);
        expect(result).toBe(154440n);
    });
    test('should return 62815650955529472000n for 100P10', () => {
        const result = permutation(1000, 100);
        expect(result).toBe(5958926632240478155489389057946132722598279588777288866613428027720091866834339557556406953783393337191792337384343797137527180562707601151082428455887739138152983603695993602780124665235348032787297990137398327480690965409929969664334240631387010833309096272433060469800960000000000000000000000000n);
    });
    test('should return undefined for fractional values', () => {
        let result = permutation(13 / 4, 5);
        expect(result).toBe(undefined);
        result = permutation(13, 5 / 4);
        expect(result).toBe(undefined);
        result = permutation(13 / 4, 5 / 4);
        expect(result).toBe(undefined);
    });
    test('should return undefined for non numerical values', () => {
        // This test is purely for javascript users who can't read docs and still want to try and calculate a permutation involving a string
        //@ts-expect-error - This is a test to make sure that the function will not accept a string
        let result = permutation('13', 5);
        expect(result).toBe(undefined);
        //@ts-expect-error - This is a test to make sure that the function will not accept a string
        result = permutation(13, '5');
        expect(result).toBe(undefined);
        //@ts-expect-error - This is a test to make sure that the function will not accept a string
        result = permutation('13', '5');
        expect(result).toBe(undefined);
    });
    test('should return undefined for n < r values', () => {
        const result = permutation(1, 5);
        expect(result).toBe(undefined);
    });
    test('should return undefined for n < 0 values', () => {
        const result = permutation(-7, 5);
        expect(result).toBe(undefined);
    });
    test('should return undefined for r < 0 values', () => {
        const result = permutation(7, -5);
        expect(result).toBe(undefined);
    });
});