diff --git a/mytodo/src/lib.rs b/mytodo/src/lib.rs
index 9204f39..4d1f70e 100644
--- a/mytodo/src/lib.rs
+++ b/mytodo/src/lib.rs
@@ -29,18 +29,18 @@ pub fn run(cli: Cli) -> Result<()> {
 
     match cli.command {
         Commands::Add { description } => {
-            tasks.add(description);
+            println!("{}", tasks.add(description)?);
             updated = true;
         }
         Commands::List => {
-            tasks.print();
+            println!("{}", tasks.print()?);
         }
         Commands::Done { id } => {
-            tasks.done(id)?;
+            println!("{}", tasks.done(id)?);
             updated = true;
         }
         Commands::Remove { id } => {
-            tasks.remove(id)?;
+            println!("{}", tasks.remove(id)?);
             updated = true;
         }
     }
diff --git a/mytodo/src/task.rs b/mytodo/src/task.rs
index 9ad7bbe..ef81747 100644
--- a/mytodo/src/task.rs
+++ b/mytodo/src/task.rs
@@ -15,6 +15,40 @@ pub struct TaskList {
 }
 
 impl TaskList {
+	pub fn add(&mut self, desc: String) -> Result<String> {
+        self.tasks.push(Task { description: desc, done: false });
+        Ok("Tugas baru ditambahkan.".to_string())
+    }
+
+    pub fn done(&mut self, id: usize) -> Result<String> {
+        if id == 0 || id > self.tasks.len() {
+            bail!("Nomor tugas {} tidak ditemukan.", id);
+        }
+        self.tasks[id - 1].done = true;
+        Ok(format!("Tugas {} ditandai selesai.", id))
+    }
+
+    pub fn remove(&mut self, id: usize) -> Result<String> {
+        if id == 0 || id > self.tasks.len() {
+            bail!("Nomor tugas {} tidak ditemukan.", id);
+        }
+        self.tasks.remove(id - 1);
+        Ok(format!("Tugas {} dihapus.", id))
+    }
+
+	pub fn print(&self) -> Result<String> {
+        if self.tasks.is_empty() {
+            return Ok("(Belum ada tugas)".to_string());
+        }
+
+        let mut output = String::from("Daftar Tugas:");
+        for (i, task) in self.tasks.iter().enumerate() {
+            let status = if task.done { "[x]" } else { "[ ]" };
+            output.push_str(&format!("\n{}. {} {}", i + 1, status, task.description));
+        }
+		Ok(output)
+    }
+
     const FILE_PATH: &'static str = "tasks.json";
 
     pub fn load() -> Result<Self> {
@@ -33,40 +67,84 @@ impl TaskList {
         fs::write(Self::FILE_PATH, data)?;
         Ok(())
     }
+}
 
-    pub fn add(&mut self, desc: String) {
-        self.tasks.push(Task { description: desc, done: false });
-        println!("Tugas baru ditambahkan.");
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_add_task() {
+        let mut list = TaskList::default();
+
+        let _ = list.add("Belajar Rust".into());
+
+        assert_eq!(list.tasks.iter().len(), 1);
+        assert_eq!(list.tasks[0].description, "Belajar Rust");
+        assert_eq!(list.tasks[0].done, false);
     }
 
-    pub fn print(&self) {
-        if self.tasks.is_empty() {
-            println!("(Belum ada tugas)");
-            return;
-        }
+    #[test]
+    fn test_done_task_success() {
+        let mut list = TaskList::default();
+        let _ = list.add("Belajar Rust".into());
 
-        println!("Daftar Tugas:");
-        for (i, task) in self.tasks.iter().enumerate() {
-            let status = if task.done { "[x]" } else { "[ ]" };
-            println!("{}. {} {}", i + 1, status, task.description);
-        }
+        let msg = list.done(1).unwrap();
+
+        assert_eq!(msg, "Tugas 1 ditandai selesai.");
+        assert_eq!(list.tasks[0].done, true);
     }
 
-    pub fn done(&mut self, id: usize) -> Result<()> {
-        if id == 0 || id > self.tasks.len() {
-            bail!("Nomor tugas {} tidak ditemukan", id);
-        }
-        self.tasks[id - 1].done = true;
-        println!("Tugas {} ditandai selesai.", id);
-        Ok(())
+    #[test]
+    fn test_done_task_failed() {
+        let mut list = TaskList::default();
+        let _ = list.add("Belajar Rust".into());
+
+        let err_msg = list.done(10).unwrap_err();
+
+        assert_eq!(err_msg.to_string(), "Nomor tugas 10 tidak ditemukan.");
+        assert_eq!(list.tasks[0].done, false);
     }
 
-    pub fn remove(&mut self, id: usize) -> Result<()> {
-        if id == 0 || id > self.tasks.len() {
-            bail!("Nomor tugas {} tidak ditemukan", id);
-        }
-        self.tasks.remove(id - 1);
-        println!("Tugas {} dihapus.", id);
-        Ok(())
+    #[test]
+    fn test_remove_task_success() {
+        let mut list = TaskList::default();
+        let _ = list.add("Belajar Rust".into());
+
+        let msg = list.remove(1).unwrap();
+
+        assert_eq!(msg, "Tugas 1 dihapus.");
+        assert_eq!(list.tasks.is_empty(), true);
     }
-}
+
+    #[test]
+    fn test_remove_task_failed() {
+        let mut list = TaskList::default();
+        let _ = list.add("Belajar Rust".into());
+
+        let err_msg = list.remove(10).unwrap_err();
+
+        assert_eq!(err_msg.to_string(), "Nomor tugas 10 tidak ditemukan.");
+        assert_eq!(list.tasks.is_empty(), false);
+    }
+
+    #[test]
+    fn test_print_empty() {
+        let list = TaskList::default();
+
+        let output = list.print().unwrap();
+        
+        assert_eq!(output, "(Belum ada tugas)");
+    }
+
+    #[test]
+    fn test_print_tasks() {
+        let mut list = TaskList::default();
+        let _ = list.add("Belajar Rust".into());
+        let _ = list.add("Belajar Unit Test".into());
+
+        let output = list.print().unwrap();
+
+        assert_eq!(output, "Daftar Tugas:\n1. [ ] Belajar Rust\n2. [ ] Belajar Unit Test");
+    }
+}
\ No newline at end of file
diff --git a/mytodo/tasks.json b/mytodo/tasks.json
index d03d74d..f789957 100644
--- a/mytodo/tasks.json
+++ b/mytodo/tasks.json
@@ -2,7 +2,7 @@
   "tasks": [
     {
       "description": "Belajar Rust",
-      "done": false
+      "done": true
     },
     {
       "description": "Belajar Kotlin",
@@ -10,7 +10,7 @@
     },
     {
       "description": "Belajar Bahasa",
-      "done": false
+      "done": true
     }
   ]
 }
\ No newline at end of file