public void testPlaceOrder() {
  doPlaceOrder(arg values here);
  // checks and assertions here for that order placement
}

public void testEnquireOrder() {
  doPlaceOrder(arg values here);
  // logic here to enquire
  // checks and assertions here for that enquiry
}

private void doPlaceOrder(parameter list here) {
  // logic to place an order here
}

These four test methods are not independent on each other so they are not testable independently. JUnit uses each testMethod as an independent test and resets (setup) the environment.

So I suggest trying this:

Order order;



public void setUp() { 
    order = .... // create an order
}

public void testPlaceOrder() { 
   // place order
   // tests on initialized order
}

public void testEnquireOrder() {
   // enquire ...
   // tests    
} 

public void testUpdateOrder()  {
   // update ...
   // tests    
} 

public void testCancelOrder()  {
   // cancel ...
   // tests    
}