jMeter Notes from Udemy course “Learn jMeter from Scratch”

I completed this Udemy course to get a different perspective of Jmeter and evaluate features that I hadn’t used previously.

The course delivered on my objectives, although the quality was poor.

Pros:
Good coverage of Jmeter features in a practical QA context
The instructor responds to Q&A and The examples worked
Good coverage for ‘new to Jmeter’ users
Cons:
Slow pace
Lack of editing where the instructor was troubleshooting and searching menus on the fly. Certain cuteness factor, though.
Section on REST and SOAP obsolete and should be updated or removed.

Here are my course notes


Sections 1 and 2 Setup, test websites and recording


Setup on Windows


Test websites
Don’t do load testing on public websites. It is not ethical and public sites will either block repeated access from the same ip address or be negatively affected.
Here are some sites that have been made available specifically for test automation development, including load testing.

Section 2 walks through recording a simple test in Firefox with jMeter’s built in Test Script Recorder, after setting network proxy from System to Manual. It also demonstrates the Blazemeter Chrome plugin. Note that the Blazemeter plugin recording requires a registration with Blazemeter and is not used in any subsequent sections.


Section 3 Thread Group and Listeners


Thread Group is a container for Controllers and Samplers and represents a number of threads or users simultaneously accessing the target system.


Listeners are elements that display a visualization of a running and completed test. Without one or more listeners there is no indication that a test is running.
The most basic listener is View Results Tree, which lists the request and response of each sampler and shows an icon representing a status code of success or error.


















Other key listeners are:
Aggregate Report: Shows statistics for the entire run















Graph Report: Shows several metrics for each sample in a run





















Section 4 Plug in Manager and Additional Thread Group options

The Plug In Manager must be added to jMeter from a link here.

A useful plug-in example is Custom Thread Groups
Concurrency Thread Group has More granularity for ramp-up than the base thread group.
























Ultimate Thread Group can assign a staged ramp up time, hold time and ramp down time

















Section 5 HTTP Cookie Manager
A Config Element of type Cookie Manager is added to store a session cookie and pass it to subsequent sampler requests. Typically the session cookie is required to be passed in a login request or other sensitive request.



Section 6 Assertions
Assertions can be added to samples or controllers to validate a response for more than a status code.
Standard assertions for an HTML response are Response Assertion, Size Assertion and Duration Assertion.
Other Assertion types cover JSON, Xpath, Bean shell etc.
Assertions can be viewed in an Assertion Results Listener


Section 7 Demo local web application

This section describes downloading an apache webserver app, Webtours, that runs a local testing website.
An account is required, it seems to be benign.

To allow Test Script Recorder to work with local Webtours, you may have to set these Firefox properties in about:config
Network.captive-portal-service.enabled" from TRUE to FALSE Network.proxy.allow_hijacking_localhost from FALSE to TRUE

Section 8 Controllers

Controllers organize samplers and permit iterative and conditional execution
Transaction Controllers group samplers and permit parameters to be applied at a group level.
Interleave Controllers group transaction controllers and alternate which controller is run.
Runtime controller will continuously run it’s contents for a specified period of time.
Recording Controller will hold all samplers created by a Test Script Recorder and is the default Target Controller

Section 9 Timers
Timers can be added to more closely emulate actual user load.
For example a Random timer can be added to moderate a sampler request from 50 requests in 1 second to 50 requests in 5 seconds.
Or a Constant Throughput Timer can generate delays to cap the maximum samples per minute that are executed.


Section 10 Regular Expression Extractor

Use Case: Script is recorded with User A credentials and the script needs to run with credentials passed as variables.
Add a Regular Expression Extractor with a variable name and a regex like .+? enclosed in ()

















Section 11 Data Driven Testing
jMeter can read input values from an external .csv file

Add a Data Element of type CSV Data Set Config to the Thread Group. No header in the csv.



Add variable names for the fields in a comma-separated list

In the sampler’s parameter list add the variable in the form ${variable-name}


















The variable is then passed in the sampler, replacing a hard-coded value that may have been collected by the script recorder
















Section 12 Handling Dynamic Responses and Correlation


Example of capturing the Session ID with a Regular Expression Extractor

An example of using the Regular Expression Extractor is capturing the session ID on navigating to a home page in a new session.
A common login pattern is to pass a session id as a hidden parameter along with username and password.
When load testing multiple logins in jMeter the session ID for each login must be captured and passed to a variable.
















Section 13 non-gui mode and reporting
jMeter can be run in an admin-mode command shell.

<path to jMeter.bat> jMeter -n -t < path to jmx file> -i <path to write result .jml file?

-n non-gui

-t test case file (.jmx)

i result file (.jml)









The .jml results file can be viewed as a spreadsheet



Alternative result reporting:
Taurus is a graphical results tool
Blazemeter is a commercial paas company that provides cloudbased load testing infrastructure that includes a graphical reporting tool


Section 14 Jmeter distributed mode.


Whereas jMeter tests are developed on standalone systems, Distrubuted systems generally used for production testing where the number of threads (users) is in the 100’s or 1000’s
Basic Architecture of a distributed system






























Steps:

#remote_hosts=127.0.0.1

remote_hosts=192.168.1.66
















On the Master machine open a test and select run -> remote start and select the ip address of the slave or start all.


On the slave machine the command window will display “Starting the test ...” and “Finished the test ...”





















The jMeter instance on the master will show the listener results for tests run on the slave machines.

























Section 15 Beanshell scripting


BeanShell is a scripting language that can run in the Java Runtime Environment. In jMeter it provides a programmic capability for tasks such as passing a dynamically randomized variable.

Monitor Beanshell output in jMeter Options -> Log Viewer.

Beanshell Hello World and jMeter variable api example.
https://jmeter.apache.org/api/index.html































A random unique value can be generated by the “epoch time’ method or by adding a Random Variable sampler.





































A BeanShell PostProcessor can be used to evaluate the response code of the previous iteration.






















Section 16 Selenium Integration


A java-based Selenium project compiled to a jar can be run within Jmeter. First copy the jar to \apache-jmeter-”ver”\lib\junit\. Then in a thread group of a jMeter project add a jUnit Request sampler.

The sampler will read the Classnames and their Test Methods of all jar files in the junit folder.

Select the Classname and Test Method from the dropdowns.

In the Thread Group set the Number of Threads and any other parameters and run.

Jmeter will execute the tests from the jar file and report results to listeners as for a jmeter-hosed project.


A limitation of this method is that a separate browser will be opened for each thread and this can limit the number or threads that can be run.


A solution is to use the HtmlUnit , a headless java-based web browser integrated with Selenium.

























Section 17 REST API load testing

This section of the Udemy course is obsolete and not worth listening to.
The summary is that a REST API can be load tested from a HTTP Request sampler where the fields are entered manually as opposed to from a Test Script Recorder.

Below is an example using openweathermap.org where a free API key can be requested



Section 18 Monitoring Server Performance

Demo using the commercial java profiler tool YourKit.