// testing addAtHead
void testAddAtHead(Tester t) {
  this.initDeque();
  t.checkExpect(deque1.header.next.data, "abc");
  deque1.addAtHead("wee");
  t.checkExpect(deque1.header.next.data, "wee");
}

// testing addHeadHelp
void testAddHeadHelp(Tester t) {
  this.initDeque();
  t.checkExpect(sentinel1.next.data, "abc");
  sentinel1.addAtHeadHelp("wee");
  t.checkExpect(sentinel1.next.data, "wee");

}


// testing addAtTail
void testAddAtTail(Tester t) {
  this.initDeque();
  t.checkExpect(deque1.header.prev.data, "def");
  deque1.addAtTail("woo");
  t.checkExpec(deque1.header.prev.data, "woo");
}

// testing addTailHelp
void testAddTailHelp(Tester t) {
  this.initDeque();
  t.checkExpect(sentinel1.prev.data, "def");
  deque1.addAtTail("woo");
  t.checkExpec(sentinel1.prev.data, "woo");
}

// testing dataGrabber
void testDataGrabber(Tester t) {
  this.initDeque();
  t.checkExpect(node1.dataGrabber(), "abc");
  t.checkExpect(node4.dataGrabber(), "def");
  t.checkExpect(sentinel1.dataGrabber(), null);
}