diff --git a/domain-model.md b/domain-model.md
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+++ b/domain-model.md
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+# Exercise 1
+
+### Class: `ShoppingBasket`
+
+| Method                   | Member variables    | Scenario          | Result                                                                        |
+|--------------------------|---------------------|-------------------|-------------------------------------------------------------------------------|
+| `double calculateCost()` | `List<Item> items`  | Basket is empty   | Return $0$                                                                    |
+|                          |                     | Basket has items  | Return total cost of the items ($>0$)                                         |
+| `void printReceipt()`    |                     | Basket is empty   | Print "empty" message                                                         |
+|                          |                     | Basket has items  | For every unique item, print name, price and quantity. Also print total cost. |
+
+### Class: `Item`
+
+| Method              | Member variables | Scenario | Result                        |
+|---------------------|------------------|----------|-------------------------------|
+| `double getprice()` | `double price`   |          | Return the price of the item. |
+| `String getName()`  | `String name`    |          | Return the name of the item.  |
+
diff --git a/src/main/java/com/booleanuk/core/Basket.java b/src/main/java/com/booleanuk/core/Basket.java
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+++ b/src/main/java/com/booleanuk/core/Basket.java
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+package com.booleanuk.core;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class Basket {
+    Map<String, Integer> items = new HashMap<>();
+
+    public boolean add(String product, int price) {
+        if (this.items.containsKey(product)) {
+            return false;
+        }
+
+        this.items.put(product, price);
+        return true;
+    }
+
+    public int total() {
+        int total = 0;
+        for (int price : this.items.values()) {
+            total += price;
+        }
+        return total;
+    }
+}
diff --git a/src/test/java/com/booleanuk/core/BasketTest.java b/src/test/java/com/booleanuk/core/BasketTest.java
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+++ b/src/test/java/com/booleanuk/core/BasketTest.java
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+package com.booleanuk.core;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.Assertions;
+
+public class BasketTest {
+    @Test
+    public void canAddNewItem() {
+        Basket basket = new Basket();
+        String product = "eggs";
+        int price = 20;
+        Assertions.assertTrue(basket.add(product, price));
+    }
+
+    @Test
+    public void cannotAddExistingItem() {
+        Basket basket = new Basket();
+        String product = "eggs";
+        int price = 20;
+        basket.add(product, price);
+        Assertions.assertFalse(basket.add(product, price));
+    }
+
+    @Test
+    public void emptyBasketShouldHaveZeroTotal() {
+        Basket basket = new Basket();
+        Assertions.assertEquals(0, basket.total());
+    }
+
+    @Test
+    public void correctCostOfSingleItem() {
+        Basket basket = new Basket();
+        String product = "eggs";
+        int price = 20;
+        basket.add(product, price);
+        Assertions.assertEquals(price, basket.total());
+    }
+
+    @Test
+    public void correctCostOfSeveralItems() {
+        Basket basket = new Basket();
+        String prod1 = "eggs";
+        String prod2 = "milk";
+        String prod3 = "flour";
+        int price1 = 20;
+        int price2 = 22;
+        int price3 = 17;
+        basket.add(prod1, price1);
+        basket.add(prod2, price2);
+        basket.add(prod3, price3);
+        Assertions.assertEquals(59, basket.total());
+    }
+
+    @Test
+    public void addingExistingItemShouldNotIncreaseTotal() {
+        Basket basket = new Basket();
+        String product = "eggs";
+        int price = 20;
+        basket.add(product, price);
+        basket.add(product, price);
+        Assertions.assertEquals(20, basket.total());
+    }
+}