What are the metrics that can be used during performance testing?

One of the most important parts that together make up the complete and effective software testing is the performance testing. Perhaps no software system or application can do without performance testing and testing of any software system or application is incomplete without this one. 

"The determination of the performance of a software system or application in terms of how and when and responsiveness and stability under different particular work loads is nothing but performance testing".

Apart from this there are several other attributes that can be taken care of by the performance testing like for example:

1. Scalability
2. Reliability
3. Resource usage and so on.

The concept of performance testing falls under the concept of performance engineering. The practice of performance testing is aimed at building the performance in to the architecture as well as design of the software system or applications before the actual coding of the software system or application begins. 

We have so many other types of testing that together make up the complete performance testing and have been mentioned below:

1. Load testing
2. Stress testing
3. Soak testing or Endurance testing
4. Spike testing
5. Isolation testing and
6. Configuration testing

Metrics used during Performance Testing

The performance testing cannot be carried out all alone by itself! Rather it is supported by some specific metrics called performance metrics. In this article we shall discuss about the metrics that are to be used during the performance testing.  We shall discuss them one by one:

 1. Average response time: 

This is the time that takes in to consideration all the response cycle ups or round trip requests until a particular point is reached and is the mean of all the response times. Response times can be measured in any of the following way:

      a) Time to last byte or 

      b) Time to first byte

   

      2. Peak response time: 

    This is similar to the previously mentioned metric and represents the longest cycle at a particular point in a particular test. Peak response time is an indication of some potential problem in our software system or application.

   

     3. Error rate: 

   The occurrence of errors under load during the processing of the requests is perhaps the most expected thing during the testing. it has been noted that the most of the errors are reported when the load on the application reaches a peak point and further from there the software system or application is not able to process any requests. Thus error rate provides a percentage of the HTTP status code responses as errors on the servers.

    

     4. Throughput: 

   This performance metric gives you a percentage of the flow of data back and forth from the servers and is measured in units of KB per second.

   

    5. Requests per second (RPS): 

    It gives a measure of the requests that are sent to the target server including requests for CSS style sheets, HTML pages, JavaScript libraries, flash files, XML documents and so on.

    6. Concurrent users: 

    This performance metric is perhaps that best way for expressing the load that is being levied on the software system or application during the performance testing. This metric is not to be equated to the RPS since there are possibilities of one user only generating a high number of requests and on the other hand a user not constantly generating requests.

     7. Cross result graphs: 

     It shows difference between post tuning and pre-tuning tests.