diff --git a/domain-model.md b/domain-model.md
new file mode 100644
index 0000000..355f640
--- /dev/null
+++ b/domain-model.md
@@ -0,0 +1,35 @@
+# Domain Model
+
+## CohortManager Class
+
+| Method                       | Member Variables             | Scenario                  | Result       |
+|------------------------------|------------------------------|---------------------------|--------------|
+|                              | ArrayList<String> cohortList |                           |              |
+| searchForCohort(String name) |                              | Name is in cohortList     | Return true  |
+|                              |                              | Name is not in cohortList | Return false |
+
+
+1.
+
+## SupermarketCashier Class
+
+| Method                                   | Member Variables | Scenario                                          | Result           |
+|------------------------------------------|------------------|---------------------------------------------------|------------------|
+|                                          | int totalCost    |                                                   |                  |
+| calculateCost(ArrayList<Item> groceries) |                  | Calculates the accumulated value of the groceries | Return totalCost |
+|                                          |                  | List is null                                      | Return -1        |
+
+
+2.
+| Method                                  | Member Variables   | Scenario                                                                 | Result |
+|-----------------------------------------|--------------------|--------------------------------------------------------------------------|--------|
+|                                         | Receipt newReceipt |                                                                          |        |
+| printReceipt(ArrayList<Item> groceries) |                    | Creates a receipt with createReceipt and prints the data to the terminal |        |
+|                                         |                    | Is unable to create a receipt. Prints error-message to the terminal      |        |
+
+| Method                                   | Member Variables   | Scenario                                                            | Result            |
+|------------------------------------------|--------------------|---------------------------------------------------------------------|-------------------|
+|                                          | Receipt newReceipt |                                                                     |                   |
+| createReceipt(ArrayList<Item> groceries) |                    | Creates a new receipt with the requested information and returns it | Return newReceipt |
+|                                          |                    | List is null                                                        | Return null       |
+
diff --git a/src/main/java/com/booleanuk/core/Basket.java b/src/main/java/com/booleanuk/core/Basket.java
new file mode 100644
index 0000000..403871b
--- /dev/null
+++ b/src/main/java/com/booleanuk/core/Basket.java
@@ -0,0 +1,19 @@
+package com.booleanuk.core;
+
+import java.util.HashMap;
+
+public class Basket {
+    HashMap<String, Integer> items = new HashMap<>();
+
+    public boolean add(String product, int price) {
+        return items.put(product, price) == null;
+    }
+
+    public int total() {
+        int totalCost = 0;
+        for(String key : items.keySet()) {
+            totalCost += items.get(key);
+        }
+        return totalCost;
+    }
+}
diff --git a/src/main/java/com/booleanuk/core/CohortManager.java b/src/main/java/com/booleanuk/core/CohortManager.java
index 48a1b26..24f9699 100644
--- a/src/main/java/com/booleanuk/core/CohortManager.java
+++ b/src/main/java/com/booleanuk/core/CohortManager.java
@@ -1,5 +1,9 @@
 package com.booleanuk.core;
 
-public class CohortManager {
+import java.util.ArrayList;
 
+public class CohortManager {
+    public boolean search(ArrayList<String> cohorts, String name) {
+        return cohorts.contains(name);
+    }
 }
diff --git a/src/test/java/com/booleanuk/core/BasketTest.java b/src/test/java/com/booleanuk/core/BasketTest.java
new file mode 100644
index 0000000..b11dfac
--- /dev/null
+++ b/src/test/java/com/booleanuk/core/BasketTest.java
@@ -0,0 +1,38 @@
+package com.booleanuk.core;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class BasketTest {
+
+    @Test
+    public void addItemThatDoesNotExist() {
+        Basket basket = new Basket();
+        Assertions.assertTrue(basket.add("milk", 2));
+    }
+
+    @Test
+    public void addItemThatAlreadyExists() {
+        Basket basket = new Basket();
+        basket.items.put("butter", 4);
+        Assertions.assertFalse(basket.add("butter", 4));
+    }
+
+    @Test
+    public void getCorrectTotalCost() {
+        Basket basket = new Basket();
+        basket.items.put("butter", 4);
+        basket.items.put("milk", 2);
+        basket.items.put("coffee", 7);
+        Assertions.assertEquals(13, basket.total());
+    }
+
+    @Test
+    public void getWrongTotalCost() {
+        Basket basket = new Basket();
+        basket.items.put("butter", 4);
+        basket.items.put("milk", 2);
+        basket.items.put("coffee", 7);
+        Assertions.assertNotEquals(10, basket.total());
+    }
+}
diff --git a/src/test/java/com/booleanuk/core/CohortManagerTest.java b/src/test/java/com/booleanuk/core/CohortManagerTest.java
index 5dea868..98a2ecd 100644
--- a/src/test/java/com/booleanuk/core/CohortManagerTest.java
+++ b/src/test/java/com/booleanuk/core/CohortManagerTest.java
@@ -3,6 +3,41 @@
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
+import java.util.ArrayList;
+
 class CohortManagerTest {
 
+    @Test
+    public void searchForCohortThatExists() {
+        // 1. Setup
+        CohortManager cohortManager = new CohortManager();
+        ArrayList<String> cohorts = new ArrayList<>() {{
+            add("JAEX1");
+            add("JAEX2");
+            add("JAEX3");
+            add("JAEX4");
+            add("JAEX5");
+        }};
+        String name = "JAEX5";
+
+        // 2. Execute / 3. Verify
+        Assertions.assertTrue(cohortManager.search(cohorts, name));
+    }
+
+    @Test
+    public void searchForCohortThatDoesNotExist() {
+        // 1. Setup
+        CohortManager cohortManager = new CohortManager();
+        ArrayList<String> cohorts = new ArrayList<>() {{
+            add("JAEX1");
+            add("JAEX2");
+            add("JAEX3");
+            add("JAEX4");
+            add("JAEX5");
+        }};
+        String name = "JAEX6";
+
+        // 2. Execute / 3. Verify
+        Assertions.assertFalse(cohortManager.search(cohorts, name));
+    }
 }