jMeter - Test Plan Elements
A JMeter Test Plan comprises of test elements which are discussed below. A Test Plan would comprise at least one Thread Group. Within each Thread Group we may place a combination of one or more of other elements: Sampler, Logic Controller, Configuration Element, Listener, and Timer. Each Sampler can be preceded by one or more Pre-processor element, followed by Post-processor element, and/or Assertion element. Let's see each of these elements in detail:
Thread Group elements are the beginning points of your test plan. As the name suggests, the thread group elements control the number of threads JMeter will use during the test. We can also control the following via the Thread Group:
By setting the number of Threads.
By setting the Ramp Up Time
By setting the number of test iterations.
The Thread Group Control Panel looks like this:
Details of each component on the above panel are:
Action to be taken after a Sampler error: In case any error occurs during test execution you may let the test either:
Continue to the next element in the test
Stop Thread to stop the current Thread.
Stop Test completely, in case you want to inspect the error before continue running.
Number of Threads: Simulates the number of user(s) or connection(s) to your server application.
Ramp-Up Period: Defines how long it will take JMeter to get all threads running.
Loop Count: Defines the number of times to execute the test.
Scheduler checkbox Once selected, the Scheduler Configuration section will appear at the bottom of the control panel.
Scheduler Configuration You can configure the start and end time of running the test.
JMeter has two types of Controllers: Samplers and Logic Controllers.
Samplers allow JMeter to send specific types of requests to a server. They simulate a user's request for a page from the target server. For example, you can add a HTTP Request sampler if you need to perform a POST, GET, DELETE on a HTTP service
Some useful samplers are:
An HTTP Request Sampler Control Panel looks like the following figure:
Logic Controllers let you control order of processing of Samplers in a Thread. Logic Controllers can change the order of request coming from any of their child elements. Some examples are: ForEach Controller, While Controller, Loop Controller, IF Controller, Run Time Controller, Interleave Controller, Throughput Controller, Run Once Controller.
A Loop Controller Control Panel looks like the following figure:
The following list consists of all the Logic Controllers JMeter provides:
Once Only Controller
Random Order Controller
Test Fragments is a special type of element placed at the same level as Thread Group element. It is distinguished from a Thread Group in that it is not executed unless it is referenced by either a Module Controller or an Include_Controller. This element is purely for code re-use within Test Plans.
Listeners let you view the results of Samplers in the form of tables, graphs, trees or simple text in some log files. They provide visual access to the data gathered by JMeter about the test cases as a Sampler component of JMeter is executed.
Listeners can be added anywhere in the test, including directly under the test plan. They will collect data only from elements at or below their level. The following list consists of all the Listeners JMeter provides:
Sample Result Save Configuration
Graph Full Results
View Results Tree
View Results in Table
Simple Data Writer
Distribution Graph (alpha)
By default, a JMeter thread will send requests without pausing between each sampler. This may not be what you want. We can add a timer element which will allow us to define a period to wait between each request.
The following list consists of all the Timers JMeter provides:
Gaussian Random Timer
Uniform Random Timer
Constant Throughput Timer
Poisson Random Time
As an example, the Constant Timer Control Panel looks like this:
Assertions allow you to include some validation test on the response of your request made using a Sampler. Using assertions you can prove that your application is returning the correct data. JMeter will highlight when an assertion fails.
The following list consists of all the Assertions JMeter provides:
XML Schema Assertion
As an example, the Response Assertion Control Panel looks like this:
Configuration Elements allow you to create defaults and variables to be used by Samplers. They are used to add or modify requests made by Samplers.
They are executed at the start of the scope of which they are part, before any Samplers that are located in the same scope. Therefore, a Configuration Element is accessed only from inside the branch where it is placed.
The following list consists of all the Configuration Elements JMeter provides:
CSV Data Set Config
FTP Request Defaults
HTTP Authorization Manager
HTTP Cache Manager
HTTP Cookie Manager
HTTP Proxy Server
HTTP Request Defaults
HTTP Header Manager
Java Request Defaults
JDBC Connection Configuration
Login Config Element
LDAP Request Defaults
LDAP Extended Request Defaults
TCP Sampler Config
User Defined Variables
Simple Config Element
A Pre-Procesor is something that will happen before a sampler executes. They are often used to modify the settings of a Sample Request just before it runs, or to update variables that are not extracted from response text.
The following list consists of all the Pre-Processor Elements JMeter provides:
HTML Link Parser
HTTP URL Re-writing Modifier
HTTP User Parameter Modifier
RegEx User Parameters
A Post Processor executes after a sampler finishes its execution. This element is most often used to process the response data, for example, to retrieve particular value for later use.The following list consists of all the Post-Processor Elements JMeter provides:
Regular Expression Extractor
Result Status Action Handler
Execution order of Test Elements
Following is the execution order of the test plan elements:
Post-Processors (unless SampleResult is null)
Assertions (unless SampleResult is null)
Listeners (unless SampleResult is null)