Debugging JMeter Tests

When creating components of a JMeter test plan, or when changing the configuration values you may find the requests are no longer successfully sent. Here are some options for debugging.

View Results Tree

The View Results Tree shows all the requests sent and responses received, including headers added by JMeter, the time it took to get the response and some response codes.
The View Results Tree can be used during debugging, but DO NOT use it during load testing as it consumes a lot of resources (memory and CPU).
To use the View Results Tree, right-click on a component to add it to (usually the Thread Group you are testing) and select Add > Listener > View Results Tree.
When you run a test, the View Results Tree will fill up with your requests:


Debug Sampler

The Debug Sampler is useful if you are working with JMeter variables and/or properties.
To use the Debug Sampler, right click on a Thread Group to add it to and select Add > Sampler > DebugSampler. Drag it to the position you want to view variables for (e.g. after a request you have extracted a value from).
When you run a test, you can view values from the Debug Sampler in the View Results Tree:


All requests sent and responses received from JMeter can be viewed in Fiddler. To make the requests visible, you may need to set the following values for each HTTP Request:


You can view the logs by selecting the following menu option:
This gives you the option to view lots of information that is written by default (Log Level is configurable in the menu above), or to use logging to debug a BeanShell script. You can write to the logs as follows:"Hello");

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Software developer from Wellington, New Zealand

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