UI

[inverse-tax] / tax.test.js

diff --git a/tax.test.js b/tax.test.js
index 27767fedc6912d48eb7be731be102919c02bd874..21b98b62a01955df27e6c9e2931c40ae66e385d9 100644 (file)
--- a/tax.test.js
+++ b/tax.test.js
@@ -60,4 +60,15 @@ test("invert", () => {
   assert.strictEqual(invert([[10, Infinity, .1]])( 9),  9);
   assert.strictEqual(invert([[0, 100, .1], [100, Infinity, .2]])(170), 200);
   assert.strictEqual(invert([[0, 100, .1], [100, Infinity, .2]])(112), 127.5);
   assert.strictEqual(invert([[10, Infinity, .1]])( 9),  9);
   assert.strictEqual(invert([[0, 100, .1], [100, Infinity, .2]])(170), 200);
   assert.strictEqual(invert([[0, 100, .1], [100, Infinity, .2]])(112), 127.5);

+  assert.strictEqual(invert([[6, 90, 0.75], [90, Infinity, 0.12]])(27), 90);
+
+  for (var i = 0; i < 1000; i++) {
+    const t = make_random_tax_table();
+    const inverted_t = invert(t);
+    for (var j = 0; j < 20; j++) {
+      const net = rand(250);
+      const gross = inverted_t(net);
+      assert.ok(near(net, gross - tax(t, gross)));
+    }
+  }

 });
 });