diff --git a/src/main/java/com/booleanuk/core/TodoList.java b/src/main/java/com/booleanuk/core/TodoList.java
index 675adaf0b..f8aa0921d 100644
--- a/src/main/java/com/booleanuk/core/TodoList.java
+++ b/src/main/java/com/booleanuk/core/TodoList.java
@@ -1,5 +1,88 @@
 package com.booleanuk.core;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
 public class TodoList {
+    HashMap<String, Boolean> todoMap = new HashMap<>();
+
+    public TodoList(HashMap<String, Boolean> map) {
+        this.todoMap = map;
+    }
+
+    public Boolean add(String task) {
+        if (task.toLowerCase().trim().isEmpty()) {
+            return false;
+        } else if (todoMap.containsKey(task.toLowerCase().trim())) {
+            return false;
+        }
+
+        todoMap.put(task, false);
+        return  true;
+    }
+
+    public HashMap<String, Boolean> getAll() {
+        return todoMap;
+    }
+
+    public ArrayList<String> getCompletedTasks() {
+        ArrayList<String> completedTasks = new ArrayList<>();
+
+        for (Map.Entry<String, Boolean> entry : todoMap.entrySet())
+            if (entry.getValue().equals(true))
+                completedTasks.add(entry.getKey());
+
+        return completedTasks;
+    }
+
+    public ArrayList<String> getIncompleteTasks() {
+        ArrayList<String> incompleteTasks = new ArrayList<>();
+
+        for (Map.Entry<String, Boolean> entry : todoMap.entrySet())
+            if (entry.getValue().equals(false))
+                incompleteTasks.add(entry.getKey());
+
+        return incompleteTasks;
+    }
+
+    public Boolean toggleStatus(String taskName) {
+        for (Map.Entry<String, Boolean> entry : todoMap.entrySet())
+            if (entry.getKey().equals(taskName.toLowerCase().trim())) {
+                entry.setValue(!entry.getValue());
+                return true;
+            }
+        return false;
+    }
+
+    public String searchForTask(String taskName) {
+        for (Map.Entry<String, Boolean> entry : todoMap.entrySet())
+            if (entry.getKey().equals(taskName.toLowerCase().trim()))
+                return "Task found.";
+        return "Task not found.";
+    }
+
+    public void removeTask(String task) {
+        for (Map.Entry<String, Boolean> entry : todoMap.entrySet())
+            if (entry.getKey().equals(task.toLowerCase().trim())) {
+                todoMap.remove(entry.getKey());
+                return;
+            }
+    }
+
+    // Can use TreeMap as return ??
+    public ArrayList<String> getAllAscending() {
+        ArrayList<String> keyList = new ArrayList<>(todoMap.keySet());
+        keyList.sort(null);
+        return keyList;
+    }
+
+    public ArrayList<String> getAllDescending() {
+        ArrayList<String> keyList = new ArrayList<>(todoMap.keySet());
+        keyList.sort(null);
+        Collections.reverse(keyList);
 
+        return keyList;
+    }
 }
diff --git a/src/main/java/com/booleanuk/core/domain-model.md b/src/main/java/com/booleanuk/core/domain-model.md
new file mode 100644
index 000000000..55454a984
--- /dev/null
+++ b/src/main/java/com/booleanuk/core/domain-model.md
@@ -0,0 +1,16 @@
+
+
+| **Class**  | **Members**                          | **Methods**                            | **Scenario**                                                                   | **Outputs**                |
+| ---------- | ------------------------------------ | -------------------------------------- |--------------------------------------------------------------------------------|----------------------------|
+| `TodoList` | `HashMap<String, Boolean> todoMap`   | `add(String name)`                     | Task is not in the list                                                        | `true`                     |
+|            |                                      |                                        | Task with same name already exists                                             | `false`                    |
+|            |                                      | `getAll()`                             | List contains tasks                                                            | `HashMap<String, Boolean>` |
+|            |                                      | `getCompleted()`                       | Some tasks are marked as complete                                              | `HashMap<String, Boolean>` |
+|            |                                      | `getIncomplete()`                      | Some tasks are incomplete                                                      | `HashMap<String, Boolean>` |
+|            |                                      | `toggleStatus(String name)`            | Task with that name exists — changes from incomplete to complete or vice versa | `true` / `false`           |
+|            |                                      | `search(String name)`                  | Task with that name exists                                                     | `"Task found"`              |
+|            |                                      |                                        | Task does not exist                                                            | `"Task not found"`         |
+|            |                                      | `remove(String name)`                  | Task removed from list                                                         | `true`                     |
+|            |                                      |                                        | Task does not exist                                                            | `false`                    |
+|            |                                      | `getAllAsc()`                          | Returns all tasks sorted by name A–Z                                           | `HashMap<String, Boolean>` |
+|            |                                      | `getAllDesc()`                         | Returns all tasks sorted Z–A                                                   | `HashMap<String, Boolean>` |
diff --git a/src/main/java/com/booleanuk/extension/Task.java b/src/main/java/com/booleanuk/extension/Task.java
new file mode 100644
index 000000000..ebe740457
--- /dev/null
+++ b/src/main/java/com/booleanuk/extension/Task.java
@@ -0,0 +1,72 @@
+package com.booleanuk.extension;
+
+import java.time.LocalDateTime;
+import java.util.Date;
+
+public class Task {
+    private int id;
+    private String name;
+    private Date creationTime;
+    private Boolean status;
+
+    public Task(int id, String name, Boolean status) {
+        this.id = id;
+        this.name = name;
+        this.creationTime = getRandomDate();
+        this.status = status;
+    }
+
+    public Date getRandomDate() {
+        long currentTime = System.currentTimeMillis();
+        // Define time range: last year (365 days)
+        long yearInMillis = 365L * 24 * 60 * 60 * 1000;
+        long randomTime = currentTime - (long)(Math.random() * yearInMillis);
+        return new Date(randomTime);
+    }
+
+    public Task() {
+
+    }
+
+    public Boolean getStatus() {
+        return status;
+    }
+
+    public void setStatus(Boolean status) {
+        this.status = status;
+    }
+
+    public void toggleStatus() {
+        this.status = !status;
+    }
+
+    public Date getCreationTime() {
+        return creationTime;
+    }
+
+    public void setCreationTime(Date creationTime) {
+        this.creationTime = creationTime;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+}
+
+//
+//I want to be able to get a task by a unique ID.
+//I want to update the name of a task by providing its ID and a new name.
+//I want to be able to change the status of a task by providing its ID.
+//I want to be able to see the date and time that I created each task.
\ No newline at end of file
diff --git a/src/main/java/com/booleanuk/extension/TodoListExtension.java b/src/main/java/com/booleanuk/extension/TodoListExtension.java
new file mode 100644
index 000000000..f31a65bc3
--- /dev/null
+++ b/src/main/java/com/booleanuk/extension/TodoListExtension.java
@@ -0,0 +1,52 @@
+package com.booleanuk.extension;
+
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.HashMap;
+
+public class TodoListExtension {
+    ArrayList<Task> taskList = new ArrayList<>();
+
+    public TodoListExtension() {
+        taskList.add(new Task(1, "task1", false));
+        taskList.add(new Task(2, "task2", false));
+        taskList.add(new Task(3, "task3", false));
+        taskList.add(new Task(4, "task4", false));
+    }
+
+    public void addTask(Task newTask) {
+        taskList.add(newTask);
+    }
+
+    public Task getTaskByID(int id) {
+        for (Task task : taskList) {
+            if (task.getId() == id) {
+                return task;
+            }
+        }
+        return null;
+    }
+
+    public void updateTask(int id, String newName) {
+        for (Task task : taskList)
+            if (task.getId() == id)
+                task.setName(newName);
+    }
+
+    public void changeStatusWithId(int id) {
+        taskList.stream()
+                .filter(task -> task.getId() == id)
+                .findFirst().map(task -> {task.toggleStatus();
+                    return null;
+                });
+    }
+
+    public Date getTaskCreationTime(String taskName) {
+        for (Task task : taskList) {
+            if (task.getName().equals(taskName)) {
+                return task.getCreationTime();
+            }
+        }
+        return null;
+    }
+}
diff --git a/src/test/java/com/booleanuk/core/TodoListTest.java b/src/test/java/com/booleanuk/core/TodoListTest.java
index 0bef779a4..4ec39483f 100644
--- a/src/test/java/com/booleanuk/core/TodoListTest.java
+++ b/src/test/java/com/booleanuk/core/TodoListTest.java
@@ -3,11 +3,157 @@
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
+import java.util.HashMap;
+import java.util.List;
+
 class TodoListTest {
+    private HashMap<String, Boolean> testmap = null;
+
+    public void loadTasks() {
+        testmap = new HashMap<>();
+        testmap.put("task1", false);
+        testmap.put("task2", false);
+        testmap.put("task3", true);
+        testmap.put("task4", false);
+        testmap.put("task5", true);
+    }
+
+    @Test
+    public void addTaskThatDoesNotExist() {
+        loadTasks();
+        TodoList list = new TodoList(testmap);
+
+        Assertions.assertFalse(list.add("Task1"));
+        Assertions.assertFalse(list.add("Task2"));
+        Assertions.assertFalse(list.add("task2"));
+        Assertions.assertTrue(list.add("Task10"));
+        Assertions.assertFalse(list.add("Task5"));
+        Assertions.assertTrue(list.add("Task20"));
+        Assertions.assertFalse(list.add("  "));
+    }
+
+    @Test
+    public void addTaskThatAlreadyExists() {
+        loadTasks();
+        TodoList list = new TodoList(testmap);
+        Assertions.assertFalse(list.add("Task1"));
+        Assertions.assertTrue(list.add("Task11"));
+        Assertions.assertFalse(list.add("task1")); // Case-sensitive
+        Assertions.assertFalse(list.add(" "));
+    }
+
+    @Test
+    public void getAllTasksReturnsMapOrEmptyMapIfNoContent() {
+        TodoList list = new TodoList(HashMap.newHashMap(0));
+        Assertions.assertEquals(0, list.getAll().size()); // Test on Empty
+
+        loadTasks();
+        TodoList list2 = new TodoList(testmap);
+        Assertions.assertEquals(5, list2.getAll().size());
+        list2.add("item6");
+        Assertions.assertEquals(6, list2.getAll().size());
+    }
+
+    @Test
+    public void getCompletedTasks() {
+        loadTasks();
+        TodoList list = new TodoList(testmap);
+
+        Assertions.assertEquals(2, list.getCompletedTasks().size());
+        list.add("task25");
+        Assertions.assertEquals(2, list.getCompletedTasks().size());
+    }
+
+    @Test
+    public void getIncompleteTasks() {
+        loadTasks();
+        TodoList list = new TodoList(testmap);
+
+        Assertions.assertEquals(3, list.getIncompleteTasks().size());
+        list.add("task25");
+        Assertions.assertEquals(4, list.getIncompleteTasks().size());
+    }
+
     @Test
-    public void exampleTest() {
-        String hello = "Hello";
-        Assertions.assertEquals("Hello", hello);
-        Assertions.assertNotEquals("Goodbye", hello);
+    public void toggleTaskStatus() {
+        loadTasks();
+        TodoList list = new TodoList(testmap);
+
+        Assertions.assertTrue(list.toggleStatus("task1"));
+        Assertions.assertFalse(list.toggleStatus("task500")); //task do not exist
+        Assertions.assertFalse(list.toggleStatus(" "));
+    }
+
+    @Test
+    public void searchForTaskWhichExists() {
+        loadTasks();
+        TodoList list = new TodoList(testmap);
+        Assertions.assertEquals("Task found.", list.searchForTask("task2"));
+        Assertions.assertEquals("Task found.", list.searchForTask("task5"));
+        Assertions.assertEquals("Task found.", list.searchForTask("Task5"));
+    }
+
+    @Test
+    public void searchForTaskThatDoesNotExist() {
+        loadTasks();
+        TodoList list = new TodoList(testmap);
+        Assertions.assertEquals("Task not found.", list.searchForTask("task22"));
+        Assertions.assertEquals("Task not found.", list.searchForTask("task5515"));
+        Assertions.assertEquals("Task not found.", list.searchForTask("task"));
+        Assertions.assertEquals("Task not found.", list.searchForTask(" "));
+    }
+
+    @Test
+    public void removeTaskWhichExists() {
+        loadTasks();
+        TodoList list = new TodoList(testmap);
+        Assertions.assertEquals(5, list.getAll().size());
+        list.removeTask("task2");
+        Assertions.assertEquals(4, list.getAll().size());
+        list.removeTask("task1");
+        Assertions.assertEquals(3, list.getAll().size());
+        list.removeTask("task5");
+        list.removeTask("task4");
+        Assertions.assertEquals(1, list.getAll().size());
     }
+
+    @Test
+    public void removeTaskThatDoNotExist() {
+        loadTasks();
+        TodoList list = new TodoList(testmap);
+
+        list.removeTask("task2");
+        Assertions.assertEquals(4, list.getAll().size());
+        list.removeTask("task10");
+        Assertions.assertEquals(4, list.getAll().size());
+        list.removeTask("");
+        Assertions.assertEquals(4, list.getAll().size());
+        list.removeTask(" ");
+        Assertions.assertEquals(4, list.getAll().size());
+    }
+
+    @Test
+    public void getTasksInAscendingOrder() {
+        testmap = new HashMap<>();
+        testmap.put("b", false);
+        testmap.put("d", false);
+        testmap.put("c", false);
+        testmap.put("a", false);
+        TodoList list = new TodoList(testmap);
+
+        Assertions.assertEquals(List.of("a", "b", "c", "d"), list.getAllAscending());
+    }
+
+    @Test
+    public void getTasksInDescendingOrder() {
+        testmap = new HashMap<>();
+        testmap.put("b", false);
+        testmap.put("d", false);
+        testmap.put("c", false);
+        testmap.put("a", false);
+        TodoList list = new TodoList(testmap);
+
+        Assertions.assertEquals(List.of("d", "c", "b", "a"), list.getAllDescending());
+    }
+
 }
diff --git a/src/test/java/com/booleanuk/extension/TodoListExtensionTest.java b/src/test/java/com/booleanuk/extension/TodoListExtensionTest.java
new file mode 100644
index 000000000..11af8a24d
--- /dev/null
+++ b/src/test/java/com/booleanuk/extension/TodoListExtensionTest.java
@@ -0,0 +1,53 @@
+package com.booleanuk.extension;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class TodoListExtensionTest {
+
+    @Test
+    public void addTaskSuccessfully() {
+        TodoListExtension todo = new TodoListExtension();
+        Task newTask = new Task(5, "task5", false);
+        todo.addTask(newTask);
+        Assertions.assertEquals("task5", todo.getTaskByID(5).getName());
+    }
+
+    @Test
+    public void getTaskByIdElseNotFoundResponse() {
+        TodoListExtension todo = new TodoListExtension();
+        Assertions.assertEquals(1, todo.getTaskByID(1).getId());
+        Task task2 = todo.getTaskByID(10);
+        Assertions.assertNull(task2);
+    }
+
+    @Test
+    public void updateTaskByIdAndName() {
+        TodoListExtension todo = new TodoListExtension();
+
+        Assertions.assertEquals("task2", todo.getTaskByID(2).getName());
+        todo.updateTask(2, "test new name");
+        Assertions.assertEquals("test new name", todo.getTaskByID(2).getName());
+    }
+
+    @Test
+    public void updateNonExistentTaskDoesNothing() {
+        TodoListExtension todo = new TodoListExtension();
+        todo.updateTask(99, "newTask");
+        Assertions.assertNull(todo.getTaskByID(99));
+    }
+
+    @Test
+    public void changeStatusByTaskId() {
+        TodoListExtension todo = new TodoListExtension();
+
+        Assertions.assertFalse(todo.getTaskByID(3).getStatus());
+        todo.changeStatusWithId(3);
+        Assertions.assertTrue(todo.getTaskByID(3).getStatus());
+        todo.changeStatusWithId(3);
+        Assertions.assertFalse(todo.getTaskByID(3).getStatus());
+        todo.changeStatusWithId(4);
+        Assertions.assertTrue(todo.getTaskByID(4).getStatus());
+    }
+
+}