--- description: Parallel testing is defined as a software testing type, which checks multiple applications or subcomponents of one application concurrently to reduce the test time. title: What is Parallel Testing? Definition, Approach, Example image: https://www.guru99.com/images/4-2016/040516_0510_ParallelTes2.png --- [Skip to content](#main) ## Parallel Testing **Parallel Testing** is a software testing type in which multiple versions or subcomponents of an application are tested with same input on different systems simultaneously to reduce test execution time. The purpose of parallel testing is finding out if legacy version and new version are behaving the same or differently and ensuring whether new version is more efficient or not. The below image demonstrate the parallel testing. [![Parallel Testing](https://www.guru99.com/images/4-2016/040516_0510_ParallelTes2.png)](https://www.guru99.com/images/4-2016/040516%5F0510%5FParallelTes2.png) ### Parallel Testing Example When any organization is moving from old system to new system, legacy data is an important part. Transferring this data is a complex process. In software testing, verifying compatibility of the newly developed system with the old system is done through “parallel testing.” [![Parallel Testing Example](https://www.guru99.com/images/4-2016/040516_0510_ParallelTes1.png)](https://www.guru99.com/images/4-2016/040516%5F0510%5FParallelTes1.png) ## Why to do Parallel Testing Parallel Testing is done due to following reason, * To make sure the new version of the application performs correctly * To make sure the consistencies are same between new and old version * To check if the data format between two versions has changed * To check the integrity of the new application For example- currently users are using 1.0 version of an application and from the month of March users are going to use another version of an application, let’s say 1.1 version. [![Parallel Testing](https://www.guru99.com/images/4-2016/040516_0510_ParallelTes3.png)](https://www.guru99.com/images/4-2016/040516%5F0510%5FParallelTes3.png) In such cases, testers need to do the parallel testing, in order to evaluate that data migration is done successfully. Also to check whether the changes in the new version does not affect the system function. The tester must verify that changes are executed properly, and the user is getting the desired output as per the requirement. ## When to do Parallel Testing Parallel testing can be used extensively when * The company moving from old system to new system * When synchronization is performed on two systems * Legacy data imported from one system to another * All the outcomes should be defined more precisely. Example, financial domain or insurance domain where the calculation is a major functionality of the system. ### RELATED ARTICLES * [ Manual Testing Tutorial ](https://www.guru99.com/manual-testing.html "Manual Testing Tutorial") * [ What is Usability Testing? Software UX ](https://www.guru99.com/usability-testing-tutorial.html "What is Usability Testing? Software UX") * [ White Box Testing – What is, Techniques, Example & Types ](https://www.guru99.com/white-box-testing.html "White Box Testing – What is, Techniques, Example & Types") * [ 9 BEST Exploratory Testing Tools (Apr 2026) ](https://www.guru99.com/exploratory-testing-tools.html "9 BEST Exploratory Testing Tools (Apr 2026)") ## How to do Parallel Testing: Complete Approach For performing parallel testing, you can simply create several project that will test a different part of the application (Slave Projects) and one project (master project) that will run these projects. Parallel Testing has two level criteria. 1. **Parallel test entry Criteria**Parallel test entry criteria define the tasks that must be satisfied before parallel testing can be efficiently executed. 2. **Parallel test exit Criteria**Parallel test exit criteria defines the successful conclusion of the parallel testing stage. Before performing parallel testing, there are few pre-condition that has to be satisfied. * Parallel test cannot begin till environment setup is done. * All pre-conditions and scenarios should be defined first * Legacy data and new data must be migrated successfully * Parallel test is not complete until all of the exit criteria have been satisfied To perform Parallel Testing, following steps should be followed **Step 1**: Run old system against newly developed system **Step 2**: Understand different between both the system **Step 3**: Go throw complete cycle using same input **Step 4**: Measure the output of newly developed system compare to the old system **Step 5**: Report cause of bug if found ## Good Practices for Parallel Testing To perform parallel testing here are few tips and tricks, which might be useful. * **Typical bugs identified in Parallel Testing** Internal logic is changed Flow of product is changed Major functionalists are modified * **How Many Cycles Should Be Required** Number of testing cycle depends upon the complexity of the module. Run multiple scenario cycles using pre-defined test data, which was pass from the previous system * **Categorizing Difference**When we run the parallel testing cycle, the results of both the new and legacy systems should be measured line by line with differences highlighted. Every difference which we captured should be defined as per the type of error. * **Type of error occurred during cycles**For errors tester should note down following things while performing parallel testing. * Entry error * Error due to the old system * Explainable or acceptable different * Unexpected error ## What is not a Parallel Testing | It is Parallel Testing | It is not Parallel Testing | | ---------------------------------------------------------------------- | ------------------------------------------- | | Testing the updated application against the previous application. | Testing one software only. | | Run the old scenario with new software with reserved input conditions. | Cross-Browser or Cross-Platform Testing. | | The aim is to find out the outcome as per the previous system. | The aim is to find out the designing issue. | | Should have knowledge of the old and newly developed system. | Know the Difference is not required. | ## Challenges of Parallel Testing * Complete product knowledge is required. * Every outcome should be tested * Need to concentrate on Data input and flow of product ## Summary * In [Software Engineering](https://www.guru99.com/what-is-software-engineering.html), Parallel testing is testing multiple applications or subcomponents of one application concurrently to reduce the test time. * It ensures that the new system is capable enough to run the software efficiently. #### Summarize this post with: ChatGPT Perplexity Grok Google AI **Stay Updated on AI** **Get Weekly AI Skills, Trends, Actionable Advice.** ##### Sign up for the newsletter Subscribe for Free You have successfully subscribed. Please check your inbox. ![AI-Newsletter](https://www.guru99.com/images/footer-email-avatar-imges-1.png)Chosen by over **350,000+** professionals [Scroll to top ](#wrapper)Scroll to top × Toggle Menu Close Search for: Search ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://www.guru99.com/#organization","name":"Guru99","sameAs":["https://www.facebook.com/Guru99Official","https://twitter.com/guru99com"],"logo":{"@type":"ImageObject","@id":"https://www.guru99.com/#logo","url":"https://www.guru99.com/images/guru99-logo-v1-150x59.png","contentUrl":"https://www.guru99.com/images/guru99-logo-v1-150x59.png","caption":"Guru99","inLanguage":"en-US"}},{"@type":"WebSite","@id":"https://www.guru99.com/#website","url":"https://www.guru99.com","name":"Guru99","publisher":{"@id":"https://www.guru99.com/#organization"},"inLanguage":"en-US"},{"@type":"ImageObject","@id":"https://www.guru99.com/images/parallel-testing.png","url":"https://www.guru99.com/images/parallel-testing.png","width":"242","height":"150","inLanguage":"en-US"},{"@type":"BreadcrumbList","@id":"https://www.guru99.com/parallel-testing.html#breadcrumb","itemListElement":[{"@type":"ListItem","position":"1","item":{"@id":"https://www.guru99.com","name":"Home"}},{"@type":"ListItem","position":"2","item":{"@id":"https://www.guru99.com/softwaretesting","name":"Software Testing"}},{"@type":"ListItem","position":"3","item":{"@id":"https://www.guru99.com/parallel-testing.html","name":"What is Parallel Testing? Definition, Approach, Example"}}]},{"@type":"WebPage","@id":"https://www.guru99.com/parallel-testing.html#webpage","url":"https://www.guru99.com/parallel-testing.html","name":"What is Parallel Testing? Definition, Approach, Example","dateModified":"2024-04-29T17:30:21+05:30","isPartOf":{"@id":"https://www.guru99.com/#website"},"primaryImageOfPage":{"@id":"https://www.guru99.com/images/parallel-testing.png"},"inLanguage":"en-US","breadcrumb":{"@id":"https://www.guru99.com/parallel-testing.html#breadcrumb"}},{"@type":"Person","@id":"https://www.guru99.com/author/thomas","name":"Thomas Hamilton","description":"I am Thomas Hamilton, a seasoned professional in software testing, specializing in crafting comprehensive guides to help you master your software testing skills.","url":"https://www.guru99.com/author/thomas","image":{"@type":"ImageObject","@id":"https://www.guru99.com/images/thomas-hamilton-author-v2-120x120.png","url":"https://www.guru99.com/images/thomas-hamilton-author-v2-120x120.png","caption":"Thomas Hamilton","inLanguage":"en-US"},"worksFor":{"@id":"https://www.guru99.com/#organization"}},{"@type":"Article","headline":"What is Parallel Testing? Definition, Approach, Example","keywords":"testing","dateModified":"2024-04-29T17:30:21+05:30","articleSection":"Software Testing","author":{"@id":"https://www.guru99.com/author/thomas","name":"Thomas Hamilton"},"publisher":{"@id":"https://www.guru99.com/#organization"},"description":"Parallel testing is defined as a software testing type, which checks multiple applications or subcomponents of one application concurrently to reduce the test time.","name":"What is Parallel Testing? Definition, Approach, Example","@id":"https://www.guru99.com/parallel-testing.html#richSnippet","isPartOf":{"@id":"https://www.guru99.com/parallel-testing.html#webpage"},"image":{"@id":"https://www.guru99.com/images/parallel-testing.png"},"inLanguage":"en-US","mainEntityOfPage":{"@id":"https://www.guru99.com/parallel-testing.html#webpage"}}]} ```