diff --git a/variants.js b/variants.js
index 07fb90f..f30bcfa 100644
--- a/variants.js
+++ b/variants.js
@@ -124,9 +124,14 @@ function variant3(classified, isVacation) {
     return payResult(3, threshold, classified, deduction);
 }
 
-// Expose globally
-window.classify = classify;
-window.classifyDuties = classifyDuties;
-window.variant1 = variant1;
-window.variant2 = variant2;
-window.variant3 = variant3;
+// Expose globally (Browser) + require-bar (Node-Tests)
+if (typeof window !== 'undefined') {
+  window.classify = classify;
+  window.classifyDuties = classifyDuties;
+  window.variant1 = variant1;
+  window.variant2 = variant2;
+  window.variant3 = variant3;
+}
+if (typeof module !== 'undefined' && module.exports) {
+  module.exports = { classify, classifyDuties, variant1, variant2, variant3, RATE_NORMAL, RATE_WEEKEND };
+}
diff --git a/variants.test.js b/variants.test.js
new file mode 100644
index 0000000..4497632
--- /dev/null
+++ b/variants.test.js
@@ -0,0 +1,48 @@
+const { test } = require('node:test');
+const assert = require('node:assert');
+const { classify, variant1, variant2, variant3 } = require('./variants');
+
+const noHolidays = { isHoliday: () => false, isDayBeforeHoliday: () => false };
+const d = (s) => new Date(s + 'T12:00:00');
+
+test('classify: echte Wochentage', () => {
+  assert.strictEqual(classify(d('2026-06-12'), noHolidays), 'fr'); // Freitag
+  assert.strictEqual(classify(d('2026-06-13'), noHolidays), 'sa'); // Samstag
+  assert.strictEqual(classify(d('2026-06-14'), noHolidays), 'so'); // Sonntag
+  assert.strictEqual(classify(d('2026-06-10'), noHolidays), 'weekday'); // Mittwoch
+});
+
+test('classify: Feiertags-Verschiebung (Mo–Do)', () => {
+  const hp = { isHoliday: (x) => x.getDate() === 4, isDayBeforeHoliday: (x) => x.getDate() === 3 };
+  assert.strictEqual(classify(d('2026-06-04'), hp), 'so'); // Do-Feiertag → so
+  assert.strictEqual(classify(d('2026-06-03'), hp), 'fr'); // Tag davor → fr
+  const sandwich = { isHoliday: (x) => x.getDate() === 4, isDayBeforeHoliday: (x) => x.getDate() === 4 };
+  assert.strictEqual(classify(d('2026-06-04'), sandwich), 'sa'); // Sandwich → sa
+});
+
+test('Juni-Fall Jizdan: V3 gewinnt mit 500 €', () => {
+  const c = { fr: 2, sa: 0, so: 0, weekday: 2 };
+  assert.strictEqual(variant3(c, false).bonus, 500); // Pool 2 abgezogen, 2 Werktage × 250
+  assert.strictEqual(variant1(c, false).eligible, false); // Werktage 2 < 3
+  assert.strictEqual(variant2(c, false).eligible, false); // kein sa
+});
+
+test('Juni-Fall Giurgiu: V1=450, V2=700, V3=750 (Gewinner V3)', () => {
+  const c = { fr: 0, sa: 1, so: 1, weekday: 3 };
+  assert.strictEqual(variant1(c, false).bonus, 450);
+  assert.strictEqual(variant2(c, false).bonus, 700);
+  assert.strictEqual(variant3(c, false).bonus, 750);
+});
+
+test('Juni-Fall Günes: keine Variante greift → 0 €', () => {
+  const c = { fr: 0, sa: 1, so: 0, weekday: 0 };
+  assert.strictEqual(variant1(c, false).eligible, false);
+  assert.strictEqual(variant2(c, false).eligible, false);
+  assert.strictEqual(variant3(c, false).eligible, false);
+});
+
+test('Urlaubsmodus halbiert Schwellen: Günes mit Urlaub → V2 greift', () => {
+  const c = { fr: 0, sa: 0.5, so: 0, weekday: 1 };
+  // Urlaub: V2 Schwelle sa≥0.5 UND weekday≥1 → greift; Abzug 0.5 sa + 1 weekday → 0 bezahlt
+  assert.strictEqual(variant2(c, true).eligible, true);
+});