From a659a4f09cf859b2a63dc5c15f0d4589220c9a83 Mon Sep 17 00:00:00 2001
From: Scott Worley <scottworley@scottworley.com>
Date: Thu, 23 May 2019 13:48:06 -0700
Subject: [PATCH] Test with normalized tax tables

---
 tax.js      |  8 ++++++--
 tax.test.js | 19 +++++++++++++------
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/tax.js b/tax.js
index d26db5f..7f32f74 100644
--- a/tax.js
+++ b/tax.js
@@ -7,11 +7,15 @@ function parse_table(as_text) {
   return as_text.trim().split('\n').map(parse_line);
 }
 
-function parse_tax_table(as_text) {
-  return parse_table(as_text).map(([start, rate], i, table) =>
+function tax_table_from_table(table) {
+  return table.map(([start, rate], i, table) =>
     [start, i < table.length - 1 ? table[i+1][0] : Infinity, rate / 100.0]);
 }
 
+function parse_tax_table(as_text) {
+  return tax_table_from_table(parse_table(as_text));
+}
+
 function sum(nums) {
   return nums.reduce((total, num) => total + num, 0);
 }
diff --git a/tax.test.js b/tax.test.js
index 48f2e0d..b495918 100644
--- a/tax.test.js
+++ b/tax.test.js
@@ -6,15 +6,22 @@ function test(description, f) {
   f();
 }
 
+function near(a, b, epsilon = 1e-6) {
+  return Math.abs(a - b) < epsilon;
+}
+
 function rand(limit = 100) {
   return Math.round(Math.random() * limit);
 }
 
-function make_random_tax_table(min_threshold) {
-  if (rand(2)) return [];
-  const start = min_threshold === undefined ? rand() : min_threshold;
-  const end = start + 1 + rand();
-  return [[start, end, rand()]].concat(make_random_tax_table(end));
+function make_random_tax_table() {
+  function make_random_table(min_threshold) {
+    if (rand(2)) return [];
+    const start = min_threshold === undefined ? rand() : min_threshold;
+    const end = start + 1 + rand();
+    return [[start, rand()]].concat(make_random_table(end));
+  }
+  return tax_table_from_table(make_random_table());
 }
 
 test("parse tax table", () => {
@@ -41,7 +48,7 @@ test("merge tax tables", () => {
     const combined = merge_tax_tables(t1, t2);
     for (var j = 0; j < 10; j++) {
       const income = rand(250);
-      assert.strictEqual(tax(t1, income) + tax(t2, income), tax(combined, income));
+      assert.ok(near(tax(t1, income) + tax(t2, income), tax(combined, income)));
     }
   }
 });
-- 
2.44.1