java - Mocking a interface with Mockito -

can please me below mock object. want write mock test case class. want mock interface

public interface orderif{     list<order> ordersfor(string type); } 

and implementation doesn't exists.

public class serviceimpl implements service {     private list <order> orders ;     private orderif orderif ; // 3rd party interface      public int getval(string type) {     //some code       // returns list of objects (orders)     orders = orderif.ordersfor(type);      // code      return orders.get(0) } 

i trying below no luck. receving nullpoinerexcetion.

public class serviceimpltest {      private list <order> ll ;      private service reqservice ;        @injectmocks      private orderif order;       @before      public void setup() throws exception {          ll = new arraylist<order> ();          ll.add(new order("buy"  ,  11 , "usd" ));          ll.add(new order("sell" ,  22 , "usd" ));          reqservice = spy(new serviceimpl());      }       @test      public void test() {         string type= "usd" ;          when(order.ordersfor(type)).thenreturn(ll);         q = reqservice.getval(type);         asserttrue(q.get().ask == 232.75);     } } 

i'm guessing order null , you're getting nullpointerexception here:

when(order.ordersfor(type)).thenreturn(ll); 

for @injectmocks work , instantiate class, you'll need add runner:

@runwith(mockitojunitrunner.class) public class serviceimpltest {     // ... } 

you don't have use runner, refer the documentation alternatives.