---
sourceDocument: Zurich Build or modify applications
sourceDocumentLink: https://www.servicenow.com/docs/r/zurich/application-development

 Release :

    - zurich

ft:locale :

    - en-US

ft:publication_title :

    - Zurich Build or modify applications

ft:clusterId :

    - cadev

bundleId :

    - cadev

workflow :

    - Development, Data, and Analytics


---

# Parallel testing

# Parallel testing {#ariaid-title1}

* Release version: Zurich
* 
* Updated July 31, 2025
* 
* ![](https://www.servicenow.com/docs/portal-asset/ico-clock) 1 minute to read

Reduce test design time by running multiple tests and test suites in parallel. Design tests to run in parallel by avoiding resource conflicts and data dependencies.  
Note:  
If two or more users are developing tests simultaneously, parallel testing reduces test design time. After test design completes, it is recommended to organize tests into a single hierarchical suite structure, and run the tests as a single base suite.

## Parallel testing limit {#parallel-testing__section_h3s_zf4_pgb}

Parallel testing enables users to run multiple automated tests simultaneously. This process continues until the number of parallel running tests is as per the following formula.

    Number of parallel tests = max(1, number of worker threads - 2)

Note:  
If your instance has 2 or less worker threads, configuration improvements review is recommended.The actual number of parallel tests that a non-production instance can support depends on the system resources that the instance has when it is provisioned. The parallel testing limit ensures that an instance always has system resources available for other non-testing tasks.

## Test waiting queue {#parallel-testing__section_ovy_bg4_pgb}

When the system reaches the parallel testing limit, it reschedules tests to run later. It
automatically places the tests back in sys_trigger until a worker thread is available to pick
them up. Each test in the waiting queue has a schedule the next time the test runs.

## Design considerations {#parallel-testing__section_jvs_bcd_qgb}

Run multiple tests and test suites in parallel to reduce test design time. Avoid resource conflicts and data dependencies by designing parallel running tests. Avoid resource conflicts and data dependencies by designing tests that rely only on newly generated or self-created data, or have mutual exclusion rules defined between tests that share resources.

Prevent resource conflicts between parallel tests
Prevent resource conflicts by running tests that create their own data. Tests that run with existing data prevent other tests that need the same data from running in parallel.  
Note:  
If you have two or more tests with resource conflicts, see [Mark tests as mutually exclusive](https://www.servicenow.com/docs/l0HKci4J4M1BlJCASNvhBQ#mutual-exclusion-rule__section_egk_ztm_thb) to create a mutual exclusion rule that prevents the tests from running in parallel.
**Related concepts**   

* [Reusable tests](https://www.servicenow.com/docs/L8qvTzvuR5Qqzd7jPPogtQ "Leverage reusable tests to simplify test maintenance and streamline the management of large tests and test suites. Reusable tests reduce redundancy, ensuring consistent and reliable test execution across your system.")
* [Mutually exclusive tests](https://www.servicenow.com/docs/l0HKci4J4M1BlJCASNvhBQ "Prevent conflicting tests from running in parallel by marking them as mutually exclusive. For example, when the system identifies tests that modify the same record, the system makes these tests mutually exclusive. You can also manually mark tests as mutually exclusive.")
* [Quick start tests](https://www.servicenow.com/docs/5lDvAdPPPST5s7OD6J9vmA "Copy and customize quick start tests provided by the ServiceNow AI Platform to validate that your instance works after you make any configuration changes. For example, if you apply an upgrade or develop an application.")
* [Performance profiling](https://www.servicenow.com/docs/DVcObepZodo0nickft4oyw#atf-perf-prof "Performance profiling allows you to do performance testing on your instances.")  
**Related tasks**   

* [Accelerate ATF tests failure resolution](https://www.servicenow.com/docs/WLKM2aaxrR~fO6O85NwSyA "Resolve ATF test failures faster using the actionable support provided by the new ATF failure insights feature. You can achieve it by accessing the Find changes since last successful run related link.")