The Test Therapist

The main goal for any performance test script simply is to work , but is this enough? I mean is it enough that your script has no errors ?

No errors do not mean that your script is working flawlessly , you may get a 200 response code but the script functionality is not working and in this case all your results are not correct.

The process of checking if you receive the correct response is called Validation.

In this article I will demonstrate the validation process using JMeter as one of the performance testing tools that is widely being used.

How to use validations in JMeter

In JMeter context menu we have a whole section called Assertions as in the image below

As you can see above there are lots of assertions available to use but we will focus on one particular called “Response Assertion”

Response Assertion

Before we start to dig more deeper let’s have an example to show when the response code doesn’t mean that the script is working correctly.

Example

Our script should do the following :

1- Open “demo.testfire.net”

2- Open the Login page

3- Do the Login with the credentials (admin/admin)

In the following 2 screen shots we will Show that having a success repose code doesn’t mean that the scenario went well.

According to the above screen shot the do Login should be done successfully and user should be already logged-in

But Actually the login didn’t happen , so this step of our scenario is not a successful one.

The reason that this step is failing is because I disabled the “HTTP cookie Manager” which is in most cases required in the login scenarios.

Let’s try to use the Response Assertion we mentioned earlier in this article and try to validate our scenario but before we do this let’s enable the Cookie manager to choose which text we can use in our validation step.

Now we have a successful login , so I think we can use the “Sign off” text as our asserion , because the sign off link will not be displayed if the user is not logged-in.

I added a response assertion as a child to the do login request , use the Text response and also put “Sign off” as the text to search for in the response.

I will do a trial with the Cookie manager on , then I will re-run the test with the cookie manager off to check that our validation (assertion) is working.

When I execute the test with the Cookie manager disabled , now we have a failed request although we have a 200 response code as shown on the following image.

Text Assertion is not the only assertion we can use but I think it is the mostly used one , and it will help you validate from the script side that you test is doing what should be done , help you have accurate results and have look about how your script and system under test is behaving.

*The JMX used in this article is uploaded here , feel free to use.

I though about it when i wanted to execute a data prepration script to generate some system ids and use them in a another script , but how can i get a certain value from the response and write to a file , CSV file specifically.

In this post i will tell you how i did it 🙂

Lets try to make it that way , we will use the random article function in wikipedia website to write the article name to a csv file , so everytime the random article is triggered JMeter will write the new article name to a CSV file.

The following will be added :

• Thread Group
• HTTP Sampler as shown below
  
• View results tree
• Regular expression extractor as a child to the HTTP Sampler
• BeanShell PostProcessor as a Child to the HTTP Sampler

Every time “https://en.wikipedia.org/wiki/Special:Random” will requested the value in title will be written to the CSV file

Regular Expression Extractor configuration will be as shown below :

One step is remaining , to write the “Article_Name” parameter value to a CSV file

BeanShell PostProcessor code will be as the following :

artname = vars.get("Article_Name");
f = new FileOutputStream("Results.csv", true);
p = new PrintStream(f);
this.interpreter.setOut(p);
print(artname);
f.close();

Our last step is to run the script with more than one iteration , let’s execute it with 3 iterations and then go to see the CSV fie contents.

Hope you find this article useful 🙂

Number of user generated from your local machine depends on your local machine specs but what if you can generate more users with number of tricks.

1. Don’t use listners

Listners consumes a lot of memory to be able to display information and do the necessary calculations , the less listners you use the more memory is available to generate users.

Use Simple Data Wriiter to store all of your run data and after the execution is finished you can get all information you need from .jtl file created.

*We have an article explaining how to use Simple data writer , see the following link

https://thetesttherapist.com/2019/01/27/save-run-results-with-simple-data-writer-in-apache-jmeter

2. Increase Java Heap Size Limit

We’re going to change the amount of memory reserved to JMeter by default to a larger size which allow JMeter to generate more users but you cannot set the memory size to be > 80% of your total system memory

Here is the default value in APache JMeter 5 , the default value is 256m

You can set a new value which is not larger than 80% of your system memory , JMeter will not lunch if you set a memory which is much higher than possible.

*You can change the heap size value when you edit  jmeter.bat file and search for “set HEAP” in notepad or any other editor.

3. Use x64 JDK and Windows

With x64 Windows and JDK you can consume more memory and have a better memory management that will help you generate more users than before.

*With all the above tricks your machine specs cannot exceed a certain boundary related to your hardware , and unfortunately we cannot calculate precisely how much a machine with a specific specs can generate and also it is differ from test to test.But these tricks help you get the max out of your machine before thinking to add a new machine to generate more or move to the cloud.

You want to execute a JMeter performance test but you don’t want to exceed a specific number of requests , is it possible?

Yes it is 🙂

What if we can get the value of the current iteration and make a condition to stop the test when reaching a specific values. This can be done as the following

Create a basic JMeter test plan with the essential samplers and listeners

Test plan will have the following :

1. Thread Group
2. Http Sampler
3. If controller
4. Test Action Sampler
5. Summary Report Listener

Thread Group run settings will be as the following :

We will put If controller and a test action as a child for it in the beginning of the test just under the Thread Group.

Everytime you call ${__counter(,)} you got the current iteration number.
in the above example we need to set a maximum of 300 requests (iterations).

“${__counter(,)}” >= 301

So why i put the condition operator to be >=301 because in case of concurrency it will be easier to check for number of iteration after you already finished your 300 iterations , give it a try if you put 300 the test will be stopped at the iteration number 299.

When the condition is true the Test Action will stop the test.

Then you have to add http request , in the example we used “https://en.wikipedia.org/wiki/Main_Page”

At the end add summary report to check the number of request and run the test

Summary

With IF Controller and Test Action you can limit your test execution maximum number of requests While you executing a duration based test with multiple threads.