title: Postman: test throws assertion error `expected null to deeply equal undefined`
body: <p>I have an API response as follows:</p>
  
  <pre><code>[
      {
          "id": 1,
          "instance_id": 1400,
          "entity_uuid": 21,
          "field": null,
          "old_value": null,
          "new_value": null,
          "kind": "C",
          "updated_by": "binish",
          "updated_dt": "2017-12-28T13:19:22.000Z"
      }
  ]
  </code></pre>
  
  <p>I want to validate the value of <code>old_value</code> field in Postman and below is the code: </p>
  
  <pre><code>var data = pm.response.json(responseBody);
  var oldValue = data.old_value;
  var nullValue = null;
  
  pm.test("Old Value is NULL", function(){
      pm.expect(nullValue).to.be.eql(oldValue);
  });
  </code></pre>
  
  <p>The test throws an error:</p>
  
  <blockquote>
    <p>"AssertionError: expected null to deeply equal undefined".</p>
  </blockquote>
  
  <p>What am I doing wrong here?</p>