JMeter - Functional Testing

Functional Testing

JMeter is found to be very useful and convenient in support of functional testing. Although JMeter is known more as a performance testing tool, functional testing elements can be integrated within the Test Plan, which was originally designed to support load testing. Many other load-testing tools provide little or none of this feature, restricting themselves to performance-testing purposes.

Besides integrating functional-testing elements along with load-testing elements in the Test Plan, you can also create a Test Plan that runs these exclusively. In other words, aside from creating a Load Test Plan, JMeter also allows you to create a Functional Test Plan. This flexibility is certainly resource-efficient for the testing project.

This chapter will give a walkthrough on how to create a Test Plan as we incorporate and/or configure JMeter elements to support functional testing. This chapter assumes that you have successfully gone through Chapter 5, and created a Test Plan for a specific target web server. We will begin the chapter with a quick overview to prepare you with a few expectations about JMeter. Later, we will create a new Test Plan similar to the Test Plan in Chapter 5, only smaller. The Test Plan we will create and run at the end of this chapter will incorporate elements that support functional testing, exclusively.

Preparing for Functional Testing

In this regard, I need to highlight that JMeter does not have a built-in browser, unlike many functional-test tools. It tests on the protocol layer, not the client layer (i.e. JavaScripts, applets, etc.) and it does not render the page for viewing. Although, by default that embedded resources can be downloaded, rendering these in the Listener | View Results Tree may not yield a 100% browser-like rendering. In fact, it may not be able to render large HTML files at all. This makes it difficult to test the GUI of an application under testing.

However, to compensate for these shortcomings, JMeter allows the tester to create assertions based on the tags and text of the page as the HTML file is received by the client. With some knowledge of HTML tags, you can test and verify any elements as you would expect them in the browser.

Unlike for a load-testing Test Plan, it is unnecessary to select a specific workload time to perform a functional test. In fact, the application you want to test may even reside locally, with your own machine acting as the "localhost" server for your web application. For this chapter, we will limit ourselves to selected functional aspects of the page that we seek to verify or assert.

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