add JUnit tests.

src/main/java/Deadline.java

@@ -2,7 +2,7 @@
 import java.time.LocalTime;
 
 
-public class Deadline extends Task{
+public class    Deadline extends Task{
     protected LocalDate date;
     protected LocalTime time;
 

src/main/java/TaskList.java

@@ -34,8 +34,8 @@ public Task getTask(int i) {
         return taskArr.get(i);
     }
 
-    public String getMostRecentTask() {
-        return taskArr.get(taskArr.size() - 1).toString();
+    public Task getMostRecentTask() {
+        return taskArr.get(taskArr.size() - 1);
     }
 
     public int getTaskListSize() {

src/main/java/Ui.java

@@ -94,7 +94,7 @@ public void printEventExample() {
 
     public void printAddAcknowledgement(TaskList taskList) {
         System.out.println("Alright, I've added this task:");
-        System.out.println(taskList.getMostRecentTask());
+        System.out.println(taskList.getMostRecentTask().toString());
         System.out.println("You now have " + taskList.getTaskListSize() + " tasks on your list");
     }
 

src/test/java/DukeTaskListTest.java

@@ -0,0 +1,27 @@
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class DukeTaskListTest {
+    TaskList taskList = new TaskList();
+
+    @Test
+    public void generateEmptyTaskListTest() {
+        assertEquals(true, taskList.isEmpty());
+    }
+
+    @Test
+    public void addTasksTest() {
+        taskList.addTask(new Todo("Finish Drawing", TaskType.TODO));
+        taskList.addTask(new Deadline("Essay ", "11/10/2020 1800", TaskType.DEADLINE));
+        taskList.addTask(new Event("Meeting ", "20/06/2020 1400-1600", TaskType.EVENT));
+        String todo = "[Todo][✘]Finish Drawing";
+        String deadline = "[Deadline][✘]Essay (by: 2020-10-11 18:00)";
+        String event = "[Event][✘]Meeting (at: 2020-06-20 14:00-16:00)";
+
+        assertEquals(todo, taskList.getTask(0).toString());
+        assertEquals(deadline, taskList.getTask(1).toString());
+        assertEquals(event, taskList.getTask(2).toString());
+    }
+
+}

src/test/java/DukeUiTest.java

@@ -0,0 +1,37 @@
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class DukeUiTest {
+    private final PrintStream standardOut = System.out;
+    private final ByteArrayOutputStream outputStreamCaptor = new ByteArrayOutputStream();
+    Ui ui = new Ui();
+
+    @BeforeEach
+    public void setUp() {
+        System.setOut(new PrintStream(outputStreamCaptor));
+    }
+
+    @Test
+    public void userCommandTest() {
+        String help = "Here are the commands you can use:\n"
+                + "1. help\n"
+                + "2. add\n"
+                + "3. list\n"
+                + "4. done\n"
+                + "5. delete\n"
+                + "6. date\n"
+                + "7. bye\n";
+        ui.printHelp();
+        assertEquals(help.trim(), outputStreamCaptor.toString().trim().replace("\r", ""));
+    }
+
+    @BeforeEach
+    public void tearDown() {
+        System.setOut(standardOut);
+    }
+}