JMeter Refresher

Again, as with my previous post, it's best to think of this as my course notes. These are meant for me to revisit and understand. I believe it's important to make your learning as accessible to you as possible. Often the way something's explained can be a barrier to your understanding, making it (usually unintentionally) sound more complicated than it actually is. Unfortunately, this puts a lot of people off learning, which is a shame. 

Firstly, I want to record the commands for reports. Note: I'm on a Linux machine. 

If you have an existing results file: sh jmeter -g somefile3.csv -o report-output/mytestreports1 -- this is really easy way to make pretty HTML reports out of existing results files. 

This is how to run the whole kit and kaboodle from the command line. You will need to have created the test in JMeter. 

sh jmeter -n -t "location of jmx test file" -l "location of result file" -e -o "location of reports folder"

And below an actual example: 

sh jmeter -n -t "TrainingHTTPTest.jmx" -l somefile9.csv -e -o "testreporting" 

It's worth noting that, apart from the test file (the one with the jmx extension), the other files, if they don't exist will be created. So you could do it again, thus:

sh jmeter -n -t "TrainingHTTPTest.jmx" -l resultfile12.csv -e -o "testreporting1"

For this simple test, the result file looks like this:

And a report, like the one above, will be created in a folder called testreporting1.

Apparently, when you're running a real-world performance test, you shouldn't be doing it from the GUI with lots of listeners, since this produces overhead. I knew this, and I know it can be important to ring every millisecond out of a performance test. 

So now to JMeter, which is where you create your case.  

You will need the following: 

• thread group (think users: this simulates the amount of users)

• a sampler to your thread group (sampler: think the request you want to make, the thing you want to do)

• a listener (you need at least one of these to have any feedback. There are quite a few to choose from depending on the format you're after). Below is a listerner showing two runs, one that failed and one that passed:

You can use the following:

• assertions (for example, the right code is returned, or a certain word appears on a page)
• config element (these run before the sampler and set up initial conditions -- usually for the whole test plan (I think). 
• pre-processors (things you want to have considered before the sampler runs)
• post-processors (essentially doing something with the response)

Order of execution of JMeter elements:

• Configuration elements
• Pre-processors
• Timers
• Samplers
• Post-processors
• Assertions
• Listeners

I went through Raghav Pal's JMeter Masterclass as a refresher course, which can be found here: 

https://www.youtube.com/watch?v=SoW2pBak1_Q

It was a good refresher course, and reminded me that I'd probably made a six course dinner of some things first time round, by which I mean I over-thought and over-complicated them. I must have been in a bad mood last time I installed the Plugins Manager because I remember it as a bit of a faff. It's actually straightforwardly downloading a jar file and putting in a specific folder (learning's all about being in the right mood):

Restart your JMeter and you'll see it under the Options menu, thus:

Performance testing is an important non-functional aspect of testing. Increasingly, customers for software are interested in questions like: How will this behave under load? How many users can I have use a single instance at one time? And more granular questions, such as how long does each process take, or how long does your web application take to move from one process to the other. Can it do parallel processing, etc? JMeter is a free open source tool to answer these question. It's also something of an industry standard. 

I ignored the part of the course that referred to BlazeMeter, preferring to use the Test Script Recorder in JMeter instead. 

The next part of the course covers using JMeter for API testing, which I'll cover in another post. 

Apache JMeter

I once had an acquaintance -- a moved-on colleague -- who worked exclusively with JMeter, or so he claimed. His job title was Performance Tester, and I was led to understand that JMeter was all about performance testing, load testing, stress testing.  I remember being somewhat surprised because at that point I had been naively oblivious to the specialist trends in IT. He had mastered one piece of software and was making a good living at it. I asked him if it was hard, and he said, "No, I just push a button, wait for the run to end, produce the report, and repeat with a different number of users. Sometimes I change the environment it's pointing at."

I asked if it was hard to set up, and he replied that he hadn't set it up. The setup had been done before he arrived. That occasionally something went wrong and he had to work out what it was and fix it, which could be fiddly and tiresome. These bumps in the road apart, he liked his job and had it down pat. 

Other than my above former colleague, I've never met anyone who likes JMeter. There are tutorials explaining how straightforward it is, how easy to master it is, how widely used it is, etc, lifting your heart and soul to the sure and certain knowledge that you, too, can become a performance guru. And then you point it at the software that is your bread and butter and it's glitch after glitch, error after error, frustration after frustration. I don't know anyone who thinks it's intuitive, Oh, and I remember the fun we had setting up the Firefox proxy for JMeter, which promised to make everything plain sailing. Except it didn't.

Perhaps you think this is just me. Sour grapes on the part of someone who couldn't get to grips with it. It truly isn't. I'm someone more than ready to blame my lack of understanding ahead of blaming the tool. No, I've discussed JMeter with many testers who have used it for its intended purpose and they've come away frustrated... and relieved when they get a break from it. 

Lest this all seem like protracted gripe, it's actually a prelude to me spending some days doing Raghav Pal's JMeter Masterclass, which can be found here: 

https://www.youtube.com/watch?v=SoW2pBak1_Q

I'm currently enjoying learning Katalon, but it's good to break it up a bit. Who knows? I may chance upon a tool that really suits me.