Key Concepts

Before you build your first test, you need to understand the building blocks of every JMeter test plan. Think of them as construction toy - each has a specific purpose, and you put them together to create complex load scenarios.

The Test Plan Tree

Everything in JMeter lives inside a Test Plan - a tree of test elements displayed in the left-hand panel of the GUI. The tree’s hierarchy matters as test elements are both hierarchical and ordered. All elements are executed mostly upside-down in the order they appear in the test plan. When it comes to hierarchy - for example if you have an Assertion at the same level as several Samplers - it will be applied to all Samplers and executed after each of them. And if you have an Assertion added as a child of a particular Sampler - it will be executed after that Sampler only. The behaviour is described in details in Scoping Rules chapter of JMeter User Manual.