output: #fixed code
                                  @Test
      //https://groups.google.com/forum/?fromgroups#!topic/jongo-user/p9CEKnkKX9Q
      public void canUpdateIntoAnArray() throws Exception {
  
          collection.insert("{friends:[{name:'Robert'},{name:'Peter'}]}");
  
          collection.update("{ 'friends.name' : 'Peter' }").with("{ $set : { 'friends.$' : #} }", new Friend("John"));
  
          Party party = collection.findOne().as(Party.class);
  
          assertThat(party.friends).onProperty("name").containsExactly("Robert", "John");
      }
input: #vulnerable code 
                                  @Test
      //https://groups.google.com/forum/?fromgroups#!topic/jongo-user/p9CEKnkKX9Q
      public void canUpdateIntoAnArray() throws Exception {
  
          collection.insert("{friends:[{name:'Robert'},{name:'Peter'}]}");
  
          collection.update("{ 'friends.name' : 'Peter' }").with("{ $set : { 'friends.$' : #} }", new Friend("John"));
  
          Friends friends = collection.findOne().as(Friends.class);
  
          assertThat(friends.friends).onProperty("name").containsExactly("Robert", "John");
      } 
                              #location 11 
                              #vulnerability type NULL_DEREFERENCE