diff --git a/.gitignore b/.gitignore
index 2cf908d076..97d9948471 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,5 +16,7 @@ bin/
 /text-ui-test/ACTUAL.txt
 text-ui-test/EXPECTED-UNIX.TXT
 
+/src/out
+
 # Ignore all .class files
 *.class
diff --git a/src/main/java/Duke.java b/src/main/java/duke/Duke.java
similarity index 87%
rename from src/main/java/Duke.java
rename to src/main/java/duke/Duke.java
index 80c8193ce0..8edfccd968 100644
--- a/src/main/java/Duke.java
+++ b/src/main/java/duke/Duke.java
@@ -1,7 +1,5 @@
+package duke;
 import java.util.Scanner;
-import duke.TaskList;
-import duke.Parser;
-import duke.Ui;
 
 public class Duke {
     public static void main(String[] args) {
diff --git a/src/main/java/duke/Storage.java b/src/main/java/duke/Storage.java
index 38ba02ae33..3b5e61b586 100644
--- a/src/main/java/duke/Storage.java
+++ b/src/main/java/duke/Storage.java
@@ -19,7 +19,7 @@ public class Storage {
 
     public Storage() {}
 
-    private String allTasksCombined(ArrayList<Task> items) {
+    String allTasksCombined(ArrayList<Task> items) {
         String res = "";
         for (Task item : items) {
             res += String.format("%s", item.saveString());
@@ -28,7 +28,7 @@ private String allTasksCombined(ArrayList<Task> items) {
         return res;
     }
 
-    private Task stringToTask(String str) throws InvalidTypeException, InvalidDataException {
+    Task stringToTask(String str) throws InvalidTypeException, InvalidDataException {
         String[] info = str.split("\\|");
         if (info.length < 3) {
             throw new InvalidDataException();
diff --git a/src/main/java/duke/TaskList.java b/src/main/java/duke/TaskList.java
index a6b2485e9e..2353f921a4 100644
--- a/src/main/java/duke/TaskList.java
+++ b/src/main/java/duke/TaskList.java
@@ -1,12 +1,9 @@
 package duke;
 
 import java.util.ArrayList;
-import java.io.FileWriter;
 import java.io.IOException;
-import java.io.PrintWriter;
 
 public class TaskList {
-    private final String line = "---------------------------------------------";
     private ArrayList<Task> items;
     private int total;
     Storage storage;
@@ -16,7 +13,7 @@ public TaskList() {
         this.items = storage.readData();
         this.total = items.size();
     }
-    
+
     public void bye() {
         try {
             storage.writeData(this.items);
diff --git a/src/test/java/duke/DukeTest.java b/src/test/java/duke/DukeTest.java
new file mode 100644
index 0000000000..06e67a25cf
--- /dev/null
+++ b/src/test/java/duke/DukeTest.java
@@ -0,0 +1,48 @@
+package duke;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class DukeTest {
+
+    TaskList t = new TaskList();
+
+    Storage s = new Storage();
+
+    @Test
+    public void invalidCommandTest() {
+        try {
+            Parser.handleInput("example hello");
+        } catch (InvalidTypeException e) {
+            assertEquals("OOPS!!! I'm sorry, but I don't know what that means :-(",
+                    e.getMessage());
+        } catch (InvalidDescriptionException e) {
+            assertEquals("OOPS!!! The description of a task cannot be empty",
+                    e.getMessage());
+        }
+    }
+
+    @Test
+    public void invalidIndexTest() {
+        try {
+            t.completeTask(-1);
+        } catch (InvalidIndexException e) {
+            assertEquals("OOPS!!! The index you have chosen is out of bounds",
+                    e.getMessage());
+        }
+    }
+
+    @Test
+    public void invalidDataTest() {
+        try {
+            s.stringToTask("example hello");
+        } catch (InvalidTypeException e) {
+            assertEquals("OOPS!!! I'm sorry, but I don't know what that means :-(",
+                    e.getMessage());
+        } catch (InvalidDataException e) {
+            assertEquals("OOPS!!! The data here is invalid!",
+                    e.getMessage());
+        }
+    }
+}
\ No newline at end of file