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Update tax tables: 2023 federal, 2022 CA
[inverse-tax] / 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 = 99) {
10 return Math.round(Math.random() * limit);
11 }
12
13 function make_random_tax_table() {
14 function make_random_table(min_threshold) {
15 if (rand(4) == 0) return [];
16 const start = min_threshold === undefined ? rand() : min_threshold;
17 const end = start + 1 + rand();
18 return [[start, rand()]].concat(make_random_table(end));
19 }
20 return tax_table_from_table(make_random_table());
21 }
22
23 test("parse tax table", () => {
24 const parsed = parse_tax_table(' 1 2\n10 4\n');
25 assert.strictEqual(parsed.length, 2);
26 assert.deepStrictEqual(parsed[0], [1, 10, .02]);
27 assert.deepStrictEqual(parsed[1], [10, Infinity, .04]);
28 });
29
30 test("sum", () => {
31 assert.strictEqual(sum([]), 0);
32 assert.strictEqual(sum([7]), 7);
33 assert.strictEqual(sum([100, 1, 10]), 111);
34 });
35
36 test("tax", () => {
37 assert.strictEqual(tax([[10, 100, .01], [100, Infinity, .1]], 150), 5.9);
38 });
39
40 test("merge tax tables", () => {
41 for (var i = 0; i < 1000; i++) {
42 const t1 = make_random_tax_table();
43 const t2 = make_random_tax_table();
44 const combined = merge_tax_tables(t1, t2);
45 for (var j = 0; j < 10; j++) {
46 const income = rand(250);
47 assert.ok(near(tax(t1, income) + tax(t2, income), tax(combined, income)));
48 }
49 }
50 });
51
52 test("invert", () => {
53 assert.strictEqual(invert([ ])(10), 10);
54 assert.strictEqual(invert([[ 0, Infinity, .1]])( 9), 10);
55 assert.strictEqual(invert([[10, Infinity, .1]])(19), 20);
56 assert.strictEqual(invert([[10, Infinity, .1]])( 9), 9);
57 assert.strictEqual(invert([[0, 100, .1], [100, Infinity, .2]])(170), 200);
58 assert.strictEqual(invert([[0, 100, .1], [100, Infinity, .2]])(112), 127.5);
59 assert.strictEqual(invert([[6, 90, 0.75], [90, Infinity, 0.12]])(27), 90);
60
61 for (var i = 0; i < 1000; i++) {
62 const t = make_random_tax_table();
63 const inverted_t = invert(t);
64 for (var j = 0; j < 20; j++) {
65 const net = rand(250);
66 const gross = inverted_t(net);
67 assert.ok(near(net, gross - tax(t, gross)));
68 }
69 }
70 });