text: var Stack = require('../src/stack');
  var assert = require('assert');
  
  describe('Stack', function() {
    it('push method increase size by 1', function() {
      var stack = new Stack();
  
      stack.push('hello');
      assert.equal(stack.size(), 1);
      stack.push('world');
      assert.equal(stack.size(), 2);
    });
    
    it('pop method decrease size by 1', function() {
      var stack = new Stack();
  
      stack.push('hello');
      stack.push('this');
      stack.push('world');
      var elem = stack.pop();
      assert.equal(stack.size(), 2);
    });
    
    it('pop method return correct value', function() {
      var stack = new Stack();
    
      stack.push('hello');
      stack.push('this');
      stack.push('world');
      assert.equal(stack.pop(), 'world');
      assert.equal(stack.pop(), 'this');
      assert.equal(stack.pop(), 'hello');
    });
    
    it('peek method return top element and not decrease stack size', function() {
      var stack = new Stack();
    
      stack.push('hello');
      stack.push('this');
      stack.push('world');
      assert.equal(stack.peek(), 'world');
      assert.equal(stack.size(), 3);
      assert.equal(stack.peek(), 'world');
      assert.equal(stack.size(), 3);
    });
  });
  