diff --git a/src/kernel/synch.rs b/src/kernel/synch.rs
index 5d56023..c94426c 100644
--- a/src/kernel/synch.rs
+++ b/src/kernel/synch.rs
@@ -64,7 +64,7 @@ impl Semaphore {
     /// - **scheduler** the scheduler which determine which thread to execute
     pub fn v(&mut self, machine: &mut Machine, scheduler: &mut Scheduler){
         let old_status = machine.interrupt.set_status(InterruptOff);
-        self.counter -= 1;
+        self.counter += 1;
         if self.waiting_queue.peek() != None {
             scheduler.ready_to_run(self.waiting_queue.pop().unwrap());
         }
@@ -150,6 +150,7 @@ impl Lock {
                 }
             } else {
                 self.free = true;
+                self.owner = None;
             }
         }
 
@@ -232,4 +233,122 @@ impl Condition {
 
     }
 
+}
+
+#[test]
+fn test_semaphore_single() {
+    // Init
+    let thread_manager = Rc::new(RefCell::new(ThreadManager::new()));
+    let mut semaphore = Semaphore::new(1, thread_manager);
+    let mut machine = Machine::init_machine();
+    let mut scheduler = Scheduler::new();
+    let thread = Rc::new(RefCell::new(Thread::new("test_semaphore")));
+    // P
+    semaphore.p(thread, &mut machine);
+    assert_eq!(semaphore.counter, 0);
+    assert!(semaphore.waiting_queue.is_empty());
+    // V
+    semaphore.v(&mut machine, &mut scheduler);
+    assert_eq!(semaphore.counter, 1);
+    assert!(semaphore.waiting_queue.is_empty());
+}
+
+#[test]
+fn test_semaphore_multiple() {
+    // Init
+    let thread_manager = Rc::new(RefCell::new(ThreadManager::new()));
+    let mut semaphore = Semaphore::new(2, Rc::clone(&thread_manager));
+    let mut machine = Machine::init_machine();
+    let mut scheduler = Scheduler::new();
+    let thread1 = Rc::new(RefCell::new(Thread::new("test_semaphore_1")));
+    let thread2 = Rc::new(RefCell::new(Thread::new("test_semaphore_2")));
+    let thread3 = Rc::new(RefCell::new(Thread::new("test_semaphore_3")));
+    // P
+    thread_manager.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread1)));
+    semaphore.p(thread1, &mut machine);
+    assert_eq!(semaphore.counter, 1);
+    assert!(semaphore.waiting_queue.is_empty());
+    
+    thread_manager.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread2)));
+    semaphore.p(thread2, &mut machine);
+    assert_eq!(semaphore.counter, 0);
+    assert!(semaphore.waiting_queue.is_empty());
+
+    thread_manager.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread3)));
+    semaphore.p(thread3, &mut machine);
+    assert_eq!(semaphore.counter, -1);
+    assert!(semaphore.waiting_queue.iter().count() == 1);
+
+    // V
+    semaphore.v(&mut machine, &mut scheduler);
+    assert_eq!(semaphore.counter, 0);
+    assert!(semaphore.waiting_queue.is_empty());
+
+    semaphore.v(&mut machine, &mut scheduler);
+    assert_eq!(semaphore.counter, 1);
+    assert!(semaphore.waiting_queue.is_empty());
+
+    semaphore.v(&mut machine, &mut scheduler);
+    assert_eq!(semaphore.counter, 2);
+    assert!(semaphore.waiting_queue.is_empty());
+}
+
+
+
+#[test]
+fn test_lock_simple() {
+    let thread_manager = Rc::new(RefCell::new(ThreadManager::new()));
+    let mut machine = Machine::init_machine();
+    let mut scheduler = Scheduler::new();
+    let thread = Rc::new(RefCell::new(Thread::new("test_lock")));
+    thread_manager.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread)));
+    let mut lock = Lock::new(Rc::clone(&thread_manager));
+
+    assert!(lock.free);
+    lock.acquire(Some(Rc::clone(&thread)), &mut machine);
+    assert!(lock.held_by_current_thread(Rc::clone(&thread)));
+
+    assert!(!lock.free);
+    lock.release(&mut machine, &mut scheduler, Rc::clone(&thread));
+    assert!(!lock.held_by_current_thread(thread));
+    assert!(lock.free);
+}
+
+#[test]
+fn test_lock_multiple() {
+    let thread_manager = Rc::new(RefCell::new(ThreadManager::new()));
+    let mut machine = Machine::init_machine();
+    let mut scheduler = Scheduler::new();
+    let thread1 = Rc::new(RefCell::new(Thread::new("test_lock1")));
+    let thread2 = Rc::new(RefCell::new(Thread::new("test_lock2")));
+    let thread3 = Rc::new(RefCell::new(Thread::new("test_lock3")));
+
+    thread_manager.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread1)));
+    let mut lock = Lock::new(Rc::clone(&thread_manager));
+
+    assert!(lock.free);
+    lock.acquire(Some(Rc::clone(&thread1)), &mut machine);
+    assert!(lock.held_by_current_thread(Rc::clone(&thread1)));
+    assert!(!lock.free);
+
+    thread_manager.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread2)));
+    lock.acquire(Some(Rc::clone(&thread2)), &mut machine);
+    thread_manager.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread1)));
+
+    
+    assert!(lock.held_by_current_thread(Rc::clone(&thread1)));
+    assert!(lock.waiting_queue.iter().count() == 1);
+    assert!(!lock.free);
+
+    lock.release(&mut machine, &mut scheduler, Rc::clone(&thread1));
+    assert!(!lock.held_by_current_thread(thread1));
+    assert!(lock.held_by_current_thread(Rc::clone(&thread2)));
+    assert!(!lock.free);
+
+    thread_manager.borrow_mut().set_g_current_thread(Some(Rc::clone(&thread2)));
+
+
+    lock.release(&mut machine, &mut scheduler, Rc::clone(&thread2));
+    assert!(!lock.held_by_current_thread(thread2));
+    assert!(lock.free);
 }
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