In some cases, it's really useful to have information about the script's current test-execution state. For example, you might want to
- Have different VUs run different test logic
- Use different data for each VU and iteration
- Figure out the stage that a test is in
To solve these issues, you can use execution context variables.
The k6/execution module exposes details about the current execution state, such as the name of the currently executed scenario, how many VUs are currently active, and more. The module provides test-execution information via three properties:
|Property||Meta-information and execution details about|
|instance||The current running k6 instance|
|scenario||The current running scenario|
|vu||The current VU and iteration|
k6 v0.34.0 introduced the k6/execution module. If you are using a version k6 that does not have this module, refer to the __VU and __ITER section.
_VU and _ITER (discouraged)
⚠️ __VU and __ITER are both global variables with execution-context information that k6 makes available to the test script.
A numeric counter with the current iteration number for a specific VU. Zero-based.
Current VU number in use. k6 assigns the value incrementally for each new VU instance, starting from one. The variable is 0 when executing the setup and teardown functions.
You can use execution-context variables to configure different test behaviors and parameterizations. A typical use case is a load test that simulates different users performing a login flow.
If you run tests in k6 Cloud, you have additional environment variables that tell you the server, load zone, and distribution of the currently running test. Read about cloud environment variables.