diff --git a/src/main/java/snowy/Deadline.java b/src/main/java/snowy/Deadline.java
index 5fafb17fe1..1e3da1ac5a 100644
--- a/src/main/java/snowy/Deadline.java
+++ b/src/main/java/snowy/Deadline.java
@@ -12,14 +12,14 @@ public Deadline(String name, String date) throws SnowyException {
         try {
             this.date = LocalDate.parse(date);
         } catch (DateTimeException e) {
-            throw new SnowyException();
+            throw new SnowyException("Wrong date format");
         }
     }
 
     @Override
     public String toString() {
         String temp = super.toString();
-        return String.format("[D]%s (by %s )", temp, date.format(super.FORMATTER));
+        return String.format("[D]%s (by %s)", temp, date.format(super.FORMATTER));
     }
 
     @Override
diff --git a/src/main/java/snowy/Event.java b/src/main/java/snowy/Event.java
index 0c531c7a01..9a7d7e20f5 100644
--- a/src/main/java/snowy/Event.java
+++ b/src/main/java/snowy/Event.java
@@ -13,7 +13,7 @@ public Event(String name, String fromDate, String toDate) throws SnowyException
             this.fromDate = LocalDate.parse(fromDate);
             this.toDate = LocalDate.parse(toDate);
         } catch (DateTimeException e) {
-            throw new SnowyException();
+            throw new SnowyException("Wrong date format");
         }
 
     }
diff --git a/src/main/java/snowy/Snowy.java b/src/main/java/snowy/Snowy.java
index e726acacc5..e58c21bfc0 100644
--- a/src/main/java/snowy/Snowy.java
+++ b/src/main/java/snowy/Snowy.java
@@ -19,6 +19,7 @@ private Snowy(String filePath) {
             this.tasks = new TaskList(storage.load());
         } catch (SnowyException e) {
             this.tasks = new TaskList();
+            System.out.println(e.getMessage());
         }
     }
 
diff --git a/src/main/java/snowy/SnowyException.java b/src/main/java/snowy/SnowyException.java
index ef7a1d729f..d00131797a 100644
--- a/src/main/java/snowy/SnowyException.java
+++ b/src/main/java/snowy/SnowyException.java
@@ -1,4 +1,7 @@
 package snowy;
 
-public class SnowyException extends Exception {
+public class SnowyException extends RuntimeException {
+    public SnowyException(String message) {
+        super(message);
+    }
 }
diff --git a/src/main/java/snowy/Storage.java b/src/main/java/snowy/Storage.java
index d5926ed74e..bfcfbe0319 100644
--- a/src/main/java/snowy/Storage.java
+++ b/src/main/java/snowy/Storage.java
@@ -25,7 +25,7 @@ public ArrayList<String> load() throws SnowyException{
 
 
         } catch (IOException e) {
-            throw new SnowyException();
+            throw new SnowyException("Unable to create new file");
         }
         return lines;
     }
@@ -36,7 +36,7 @@ public void save(String saveLines) throws SnowyException{
             writer.write(saveLines);
             writer.close();
         } catch (IOException e) {
-            throw new SnowyException();
+            throw new SnowyException("Unable to update file");
         }
     }
 
diff --git a/src/main/java/snowy/Task.java b/src/main/java/snowy/Task.java
index 1948b04414..a252bedab7 100644
--- a/src/main/java/snowy/Task.java
+++ b/src/main/java/snowy/Task.java
@@ -3,7 +3,7 @@
 import java.time.format.DateTimeFormatter;
 import java.time.format.FormatStyle;
 
-public class Task {
+abstract public class Task {
     private boolean isCompleted = false;
 
     public final DateTimeFormatter FORMATTER = DateTimeFormatter.ofLocalizedDate(FormatStyle.LONG);
diff --git a/src/main/java/snowy/TaskList.java b/src/main/java/snowy/TaskList.java
index 7344201182..4ca052e58c 100644
--- a/src/main/java/snowy/TaskList.java
+++ b/src/main/java/snowy/TaskList.java
@@ -73,7 +73,7 @@ private void initializeTask(String description) {
 
     public  void addToDo(String description) throws SnowyException{
         if (description.isEmpty()) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid input for Todo");
         }
         Task newTask = new ToDo(description);
         tasks.add(newTask);
@@ -82,23 +82,23 @@ public  void addToDo(String description) throws SnowyException{
 
     public void addDeadline(String description) throws SnowyException{
         if (description.isEmpty()) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid input for Deadline");
         }
 
         int byIndex = description.indexOf("/by ");
 
         if (byIndex == -1) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid input for Deadline");
         }
         String deadlineName = description.substring(0, byIndex).trim();
         String date = description.substring(byIndex + 4);
 
         if (deadlineName.isEmpty()) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid input for Deadline");
         }
 
         if (date.isEmpty()) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid input for Deadline");
         }
         Task newTask = new Deadline(deadlineName, date);
         tasks.add(newTask);
@@ -107,26 +107,26 @@ public void addDeadline(String description) throws SnowyException{
 
     public void addEvent(String description) throws SnowyException{
         if (description.isEmpty()) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid input for Event");
         }
         int fromIndex = description.indexOf("/from ");
         int toIndex = description.indexOf("/to ");
 
         if (toIndex == -1 || fromIndex == -1) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid input for Event");
         }
 
         String eventName = description.substring(0, fromIndex);
         String fromDate = description.substring(fromIndex + 6, toIndex).trim();
         String toDate = description.substring(toIndex + 4);
         if (eventName.isEmpty()) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid input for Event");
         }
         if (fromDate.isEmpty()) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid input for Event");
         }
         if (toDate.isEmpty()) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid input for Event");
         }
         Task newTask = new Event(eventName, fromDate, toDate);
         tasks.add(newTask);
@@ -137,7 +137,7 @@ public Task deleteTask(int index) throws SnowyException {
         try {
             return tasks.remove(index - 1);
         } catch (IndexOutOfBoundsException e) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid index input");
         }
     }
 
@@ -146,7 +146,7 @@ public Task markTask(int index) throws SnowyException {
             tasks.get(index - 1).markComplete();
             return tasks.get(index - 1);
         } catch (IndexOutOfBoundsException e) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid index input");
         }
     }
 
@@ -155,7 +155,7 @@ public Task unmarkTask(int index) throws SnowyException {
             tasks.get(index - 1).markIncomplete();
             return tasks.get(index - 1);
         } catch (IndexOutOfBoundsException e) {
-            throw new SnowyException();
+            throw new SnowyException("Invalid index input");
         }
     }
 
diff --git a/src/test/java/snowy/DeadlineTest.java b/src/test/java/snowy/DeadlineTest.java
new file mode 100644
index 0000000000..21a36857ff
--- /dev/null
+++ b/src/test/java/snowy/DeadlineTest.java
@@ -0,0 +1,30 @@
+package snowy;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.fail;
+
+public class DeadlineTest {
+
+    @Test
+    public void toString_normalName_success() {
+        assertEquals("[D][ ] Return Book (by September 11, 2024)",
+                new Deadline("Return Book", "2024-09-11").toString());
+    }
+
+    @Test
+    public void toFileStorage_normalName_success() {
+        assertEquals("D|0|Return Book|2024-09-11",
+                new Deadline("Return Book", "2024-09-11").toFileStorage());
+    }
+
+    @Test void constructor_invalidDate_exceptionThrown() {
+        try {
+            new Deadline("Return book", "12-123-1234");
+            fail();
+        } catch (SnowyException e) {
+            assertEquals("Wrong date format", e.getMessage());
+        }
+    }
+}
diff --git a/src/test/java/snowy/EventTest.java b/src/test/java/snowy/EventTest.java
new file mode 100644
index 0000000000..35940893e0
--- /dev/null
+++ b/src/test/java/snowy/EventTest.java
@@ -0,0 +1,29 @@
+package snowy;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.fail;
+
+public class EventTest {
+    @Test
+    public void toString_normalName_success() {
+        assertEquals("[E][ ] Orientation Camp (from September 11, 2024 to: September 12, 2024)",
+                new Event("Orientation Camp", "2024-09-11", "2024-09-12").toString());
+    }
+
+    @Test
+    public void toFileStorage_normalName_success() {
+        assertEquals("[E][ ] Orientation Camp (from September 11, 2024 to: September 12, 2024)",
+                new Event("Orientation Camp", "2024-09-11", "2024-09-12").toString());
+    }
+
+    @Test void constructor_invalidDate_exceptionThrown() {
+        try {
+            new Event("Return book", "12-123-1234", "12-123-1234");
+            fail();
+        } catch (SnowyException e) {
+            assertEquals("Wrong date format", e.getMessage());
+        }
+    }
+}
diff --git a/src/test/java/snowy/ParserTest.java b/src/test/java/snowy/ParserTest.java
new file mode 100644
index 0000000000..41734da3ed
--- /dev/null
+++ b/src/test/java/snowy/ParserTest.java
@@ -0,0 +1,16 @@
+package snowy;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+public class ParserTest {
+    @Test
+    public void parse_allCapitalCommand_returnLowerCase() {
+        assertArrayEquals(new String[] {"todo", "read book"}, Parser.parse("TODO read book"));
+    }
+
+    public void parse_capitalDescription_retainCapital() {
+        assertArrayEquals(new String[] {"todo", "Read Book"}, Parser.parse("todo Read Book"));
+    }
+}
diff --git a/src/test/java/snowy/TaskListTest.java b/src/test/java/snowy/TaskListTest.java
new file mode 100644
index 0000000000..b6023e009d
--- /dev/null
+++ b/src/test/java/snowy/TaskListTest.java
@@ -0,0 +1,101 @@
+package snowy;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.fail;
+
+public class TaskListTest {
+
+    @Test
+    public void toString_correctInput_success() {
+        ArrayList<String> lines = new ArrayList<>();
+        lines.add("T|1|read book");
+        lines.add("D|0|return book|2024-09-05");
+        lines.add("E|0|Camp|2024-09-01|2024-09-02");
+        TaskList tasks = new TaskList(lines);
+
+        assertEquals("1. [T][X] read book\n" +
+                "2. [D][ ] return book (by September 5, 2024)\n" +
+                "3. [E][ ] Camp (from September 1, 2024 to: September 2, 2024)\n"
+                , tasks.toString());
+    }
+
+    @Test
+    public void toSaveString_correctInput_success() {
+        ArrayList<String> lines = new ArrayList<>();
+        lines.add("T|1|read book");
+        lines.add("D|0|return book|2024-09-05");
+        lines.add("E|0|Camp|2024-09-01|2024-09-02");
+        TaskList tasks = new TaskList(lines);
+
+        assertEquals("T|1|read book\n" +
+                "D|0|return book|2024-09-05\n" +
+                "E|0|Camp|2024-09-01|2024-09-02\n"
+                , tasks.toSaveString());
+    }
+
+    @Test
+    public void addToDo_correctInput_success() {
+        TaskList tasks = new TaskList();
+        tasks.addToDo("Read Book");
+
+        assertEquals("1. [T][ ] Read Book\n", tasks.toString());
+    }
+
+    @Test
+    public void addToDo_invalidInput_exceptionThrown() {
+        try {
+            TaskList tasks = new TaskList();
+            tasks.addToDo("");
+            fail();
+        } catch (SnowyException e) {
+            assertEquals("Invalid input for Todo", e.getMessage());
+        }
+    }
+
+    @Test
+    public void addDeadline_correctInput_success() {
+        TaskList tasks = new TaskList();
+        tasks.addDeadline("Return Book /by 2024-09-05");
+
+        assertEquals("1. [D][ ] Return Book (by September 5, 2024)\n", tasks.toString());
+    }
+
+    @Test
+    public void addDeadline_emptyInput_exceptionThrown() {
+        try {
+            TaskList tasks = new TaskList();
+            tasks.addDeadline("");
+            fail();
+        } catch (SnowyException e) {
+            assertEquals("Invalid input for Deadline", e.getMessage());
+        }
+    }
+
+    @Test
+    public void addDeadline_missingBy_exceptionThrown() {
+        try {
+            TaskList tasks = new TaskList();
+            tasks.addDeadline("Return book 2024-09-05");
+            fail();
+        } catch (SnowyException e) {
+            assertEquals("Invalid input for Deadline", e.getMessage());
+        }
+    }
+
+    @Test
+    public void addDeadline_InvalidDate_exceptionThrown() {
+        try {
+            TaskList tasks = new TaskList();
+            tasks.addDeadline("Return book /by 123-09-05");
+            fail();
+        } catch (SnowyException e) {
+            assertEquals("Wrong date format", e.getMessage());
+        }
+    }
+
+
+}
diff --git a/src/test/java/snowy/ToDoTest.java b/src/test/java/snowy/ToDoTest.java
new file mode 100644
index 0000000000..e82b723075
--- /dev/null
+++ b/src/test/java/snowy/ToDoTest.java
@@ -0,0 +1,16 @@
+package snowy;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+public class ToDoTest {
+    @Test
+    public void toString_normalName_success() {
+        assertEquals("[T][ ] Read Book",new ToDo("Read Book").toString());
+    }
+
+    @Test
+    public void toFileStorage_normalName_success() {
+        assertEquals("T|0|Read Book",new ToDo("Read Book").toFileStorage());
+    }
+}