From 3443c1c65e9f1753e1e656b35d08416c1fa298f2 Mon Sep 17 00:00:00 2001
From: godosa <godosa@godosa.eu>
Date: Wed, 7 Oct 2026 00:14:38 +0200
Subject: worldmap-viewer: initial public history

---
 viewer/tests/sky.test.mjs | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 viewer/tests/sky.test.mjs

(limited to 'viewer/tests/sky.test.mjs')

diff --git a/viewer/tests/sky.test.mjs b/viewer/tests/sky.test.mjs
new file mode 100644
index 0000000..836508b
--- /dev/null
+++ b/viewer/tests/sky.test.mjs
@@ -0,0 +1,38 @@
+import './_planet.mjs';
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { subsolar, sunVec, dayFraction, seasonName, DAY_MOMENTS } from '../js/sky.js';
+import { toLatLon } from '../js/geo.js';
+
+const near = (a, b, eps) => assert.ok(Math.abs(a - b) <= eps, `${a} vs ${b}`);
+
+test('sub-solar latitude follows the 20° tilt over the 216-day year', () => {
+  near(subsolar(0, 0).lat, 0, 1e-9);
+  near(subsolar(54, 0).lat, 20, 1e-9);
+  near(subsolar(108, 0).lat, 0, 1e-9);
+  near(subsolar(162, 0).lat, -20, 1e-9);
+});
+
+test('sub-solar longitude: noon at 0° at moment 23,328, midnight at 0° at moment 0', () => {
+  near(subsolar(0, DAY_MOMENTS / 2).lon, 0, 1e-9);
+  near(Math.abs(subsolar(0, 0).lon), 180, 1e-9);
+  near(subsolar(0, DAY_MOMENTS / 4).lon, 90, 1e-9);
+  const v = toLatLon(sunVec(54, DAY_MOMENTS / 2));
+  near(v.lat, subsolar(54, DAY_MOMENTS / 2).lat, 1e-6);
+});
+
+test('day length', () => {
+  near(dayFraction(0, 30), 0.5, 1e-9);
+  assert.equal(dayFraction(80, 54), 1);
+  assert.equal(dayFraction(80, 162), 0);
+  assert.equal(dayFraction(-80, 54), 0);
+  assert.equal(dayFraction(90, 0), 0.5);
+  assert.ok(dayFraction(45, 54) > 0.5 && dayFraction(45, 162) < 0.5);
+});
+
+test('season names near the equinoxes and solstices only', () => {
+  assert.equal(seasonName(0), 'northern spring equinox');
+  assert.equal(seasonName(55), 'northern midsummer');
+  assert.equal(seasonName(215), 'northern spring equinox');
+  assert.equal(seasonName(30), '');
+});
-- 
cgit