git.scottworley.com Git - inverse-tax/blob - tax.test.js

   1 "use strict";
   2
   3 var assert = require('assert');
   4
   5 function test(description, f) {
   6   f();
   7 }
   8
   9 function rand(limit = 100) {
  10   return Math.round(Math.random() * limit);
  11 }
  12
  13 function make_random_tax_table(min_threshold) {
  14   if (rand(2)) return [];
  15   const start = min_threshold === undefined ? rand() : min_threshold;
  16   const end = start + 1 + rand();
  17   return [[start, end, rand()]].concat(make_random_tax_table(end));
  18 }
  19
  20 test("parse tax table", () => {
  21   const parsed = parse_tax_table(' 1  2\n10  4\n');
  22   assert.strictEqual(parsed.length, 2);
  23   assert.deepStrictEqual(parsed[0], [1, 10, .02]);
  24   assert.deepStrictEqual(parsed[1], [10, Infinity, .04]);
  25 });
  26
  27 test("sum", () => {
  28   assert.strictEqual(sum([]), 0);
  29   assert.strictEqual(sum([7]), 7);
  30   assert.strictEqual(sum([100, 1, 10]), 111);
  31 });
  32
  33 test("tax", () => {
  34   assert.strictEqual(tax([[10, 100, .01], [100, Infinity, .1]], 150), 5.9);
  35 });
  36
  37 test("merge tax tables", () => {
  38   for (var i = 0; i < 1000; i++) {
  39     const t1 = make_random_tax_table();
  40     const t2 = make_random_tax_table();
  41     const combined = merge_tax_tables(t1, t2);
  42     for (var j = 0; j < 10; j++) {
  43       const income = rand(250);
  44       assert.strictEqual(tax(t1, income) + tax(t2, income), tax(combined, income));
  45     }
  46   }
  47 });
  48
  49 test("invert", () => {
  50   assert.strictEqual(invert([                  ])(10), 10);
  51   assert.strictEqual(invert([[ 0, Infinity, .1]])( 9), 10);
  52   assert.strictEqual(invert([[10, Infinity, .1]])(19), 20);
  53   assert.strictEqual(invert([[0, 100, .1], [100, Infinity, .2]])(170), 200);
  54 });