text: let linkedList;
  
  beforeEach(function() {
      linkedList = new LinkedList();
  });
  
  it('basic', function() {
      expect(linkedList.push(5)).to.equal(1);
      expect(linkedList.push(4)).to.equal(2);
      expect(linkedList.toArr()).to.eql([5, 4]);
  
      expect(linkedList.pop()).to.equal(4);
      expect(linkedList.pop()).to.equal(5);
      expect(linkedList.pop()).to.be.an.undefined;
      expect(linkedList.size).to.equal(0);
      expect(linkedList.toArr()).to.eql([]);
  
      expect(linkedList.unshift(5)).to.equal(1);
      expect(linkedList.unshift(4)).to.equal(2);
      expect(linkedList.toArr()).to.eql([4, 5]);
  
      expect(linkedList.shift()).to.equal(4);
      expect(linkedList.shift()).to.equal(5);
      expect(linkedList.shift()).to.be.an.undefined;
      expect(linkedList.size).to.equal(0);
      expect(linkedList.toArr()).to.eql([]);
  
      linkedList.push(5);
      linkedList.push(4);
      const node = linkedList.tail;
      linkedList.push(3);
      expect(linkedList.find(value => value === 4)).to.equal(node);
      linkedList.rmNode(node);
      expect(linkedList.toArr()).to.eql([5, 3]);
  });
  
  it('forEach', function() {
      linkedList.push(1);
      linkedList.push(2);
      linkedList.push(3);
      linkedList.push(4);
  
      let sum = 0;
  
      linkedList.forEach(function(val) {
          sum += val;
      });
  
      expect(sum).to.equal(10);
  });
  