diff --git a/src/model/Hand.js b/src/model/Hand.js
new file mode 100644
index 0000000..33a65ec
--- /dev/null
+++ b/src/model/Hand.js
@@ -0,0 +1,33 @@
+
+export class Hand {
+    /** @param {Card[]} cards */
+    constructor(cards) {
+        this.cards = cards.slice();
+        this._sortCards();
+    }
+
+    *[Symbol.iterator](){
+        for (const card of this.cards) {
+            yield card;
+        }
+    }
+
+    /** @param {Card} card */
+    play(card) {
+        const index = this.cards.indexOf(card);
+        if (-1 === index) {
+            throw new Error(`This hand does not contain the card ${card.name}`);
+        }
+        this.cards.splice(index, 1);
+    }
+
+    /** @param {Card} card */
+    add(card) {
+        this.cards.push(card);
+        this._sortCards();
+    }
+
+    _sortCards() {
+        this.cards.sort((a, b) => a.order - b.order);
+    }
+}
diff --git a/src/model/Hand.test.js b/src/model/Hand.test.js
index 32bd2b5..3f22038 100644
--- a/src/model/Hand.test.js
+++ b/src/model/Hand.test.js
@@ -1,34 +1,17 @@
 import {
-    ORDER_2_CENTER_CARD, ORDER_2_LEFT_CARD,
-    ORDER_2_RIGHT_CARD, ORDER_3_CENTER_CARD,
-    ORDER_3_LEFT_CARD, ORDER_3_RIGHT_CARD,
+    ORDER_2_CENTER_CARD,
+    ORDER_2_LEFT_CARD,
+    ORDER_2_RIGHT_CARD,
+    ORDER_3_CENTER_CARD,
+    ORDER_3_LEFT_CARD,
+    ORDER_3_RIGHT_CARD,
     ORDER_4_CENTER_CARD,
     ORDER_4_LEFT_CARD,
     ORDER_4_RIGHT_CARD
 } from "./cards.js";
 import { Deck } from "./deck.js";
+import { Hand } from "./Hand.js";
 
-class Hand {
-    /** @param {Card[]} cards */
-    constructor(cards) {
-        this.cards = cards.slice();
-        this.cards.sort((a, b) => a.order - b.order);
-    }
-
-    *[Symbol.iterator](){
-        for (const card of this.cards) {
-            yield card;
-        }
-    }
-
-    play(card) {
-        const index = this.cards.indexOf(card);
-        if (-1 === index) {
-            throw new Error(`This hand does not contain the card ${card.name}`);
-        }
-        this.cards = this.cards.splice(index, 1);
-    }
-}
 
 describe('A hand of cards', () => {
 
@@ -38,13 +21,14 @@ describe('A hand of cards', () => {
         ORDER_2_LEFT_CARD, ORDER_2_CENTER_CARD, ORDER_2_RIGHT_CARD,
     ]);
 
-    const hand = new Hand([ORDER_4_RIGHT_CARD, ORDER_4_LEFT_CARD, ORDER_4_CENTER_CARD]);
 
     test('enumerating card in order', () => {
+        const hand = new Hand([ORDER_4_RIGHT_CARD, ORDER_4_LEFT_CARD, ORDER_4_CENTER_CARD]);
+
         expect([...hand]).toEqual([ORDER_4_LEFT_CARD, ORDER_4_CENTER_CARD, ORDER_4_RIGHT_CARD,])
     });
 
-    xtest('playing a card', () => {
+    test('playing a card', () => {
         const hand = new Hand([ORDER_4_LEFT_CARD, ORDER_4_CENTER_CARD, ORDER_4_CENTER_CARD]);
 
         hand.play(ORDER_4_CENTER_CARD);
@@ -53,6 +37,10 @@ describe('A hand of cards', () => {
     });
 
     test('adding a card', () => {
+        const hand = new Hand([ORDER_4_LEFT_CARD, ORDER_4_CENTER_CARD]);
+
+        hand.add(ORDER_3_LEFT_CARD);
 
+        expect([...hand]).toEqual([ORDER_4_LEFT_CARD, ORDER_3_LEFT_CARD, ORDER_4_CENTER_CARD])
     });
 });
diff --git a/src/model/game.js b/src/model/game.js
index 990b19f..946e450 100644
--- a/src/model/game.js
+++ b/src/model/game.js
@@ -17,7 +17,7 @@ import { Unit } from "./units.js";
 
 /**
  * @param {Scenario} scenario
- * @param {{roll(number):DiceResult[]}} dice
+ * @param {{roll(a: number):DiceResult[]}} dice
  * @returns {Game}
  */
 export default function makeGame(scenario, dice = new Dice()) {