Parallel Testing

Parallel Testing
Parallel testing is an important software testing technique, which involves testing of multiple applications or the subcomponents of an application concurrently, to reduce the time & efforts of testing. Parallel testing helps verify the compatibility of the newly developed system with the old system.

During this type of testing, tester runs two different versions of software concurrently with same input. Their aim is to find out whether the legacy system and the new system are behaving similarly or in a different manner. By doing so, software testers ensure that the new system is capable enough to run the software efficiently.

Parallel Testing Features:

Parallel tests consist of two or more parts –projects or project suites -that check different components or functional characteristics of an application. These parts are executed on individual computers simultaneously and they make sure that they are functioning properly and are providing accurate results.

Other features that can help us understand parallel testing better are:

  • Parallel testing is a ticket to faster testing, which further leads to a quicker turnaround in software developments.
  • It has the ability to test more than one application part "in parallel", which allows testers to significantly reduce the test time and test their applications more efficiently.
  • The process of parallel testing is automated, and it often runs on virtual machines.
  • For the QA professional, no additional effort is required once the appropriate test scripts have been developed and all that the testing solution needs is the test suite and a pool of resources.
  • The main objective of parallel testing is to transform the old versions of an application into new versions and to test the application concurrently, so that the time required to test the software application is reduced.
  • It is helpful in cross browser & compatibility testing, version assessment, linguistic review, context validation, performance checks, environment configuration verification, localization & internationalization testing.
Parallel Testing

Reasons for Parallel Testing

With the assistance of parallel testing, software engineers can easily conduct testing on the whole system or part of the system and ensure their functionality, quality and other special qualities that make it appropriate for users. Moreover, parallel testing helps large organisations in conducting large scale testing, which further helps their business and improves their statistics. Other reasons for performing parallel testing are:

  • Parallel testing helps large organisations in conducting large scale testing, which further helps their business processes and improves their statistics.
  • Conducts redundant testing to ensure that the new version of application performs correctly and as per the requirements of the clients.
  • It demonstrates consistencies and inconsistencies between the old and the new version.
  • Ensures the integrity of the new application.
  • Verifies if the data format between the two versions have changed.

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When to Perform Parallel Tests or Parallel Testing?

After understanding the basics of parallel testing, it is essential for us to know when and how parallel testing is conducted. Therefore, listed below are the instances when parallel testing is implemented.

  • Primarily parallel testing is conducted when there is uncertainty regarding correctness of the processing of new applications, where the new and old version are similar.
  • Moreover, it is required in financial applications, such as banking where there are many similar applications, whose processing can be verified for old and new version through parallel testing.
  • Also when the organization is moving from old system to new system.
  • It is conducted when two systems are synchronized by the team of software engineers.
  • Parallel testing is used when legacy data is imported from one system to another.

Steps for Parallel Testing:

The process of parallel testing can be performed accurately by the testing team if they adopt a set of steps that ensure its accuracy and that guarantee expected results. These steps for parallel testing are:

  • The testers should ensure that they run the old and new system application versions simultaneously.
  • The difference between both the systems should be evaluated properly.
  • If there is any difference between the aforementioned systems, then the testers ought to go through the whole life cycle again, by providing the same input.
  • Once the above mentioned steps are completed, the provided output is evaluated.


Apart from testing multiple applications or subcomponents of one application concurrently to reduce the test time, parallel testing provides its users several other advantages, which make it an effective as well as profitable type of software testing. Parallel testing is a ticket to faster testing and a quicker turn around in developments. It is a type of testing that allows testers to get more testing done in a tighter window of time. Hence, the other benefits of parallel testing are mentioned below:

  • Test for Wider Compatibility: Because parallel testing is faster, it allows you to test for wider compatibility in the same amount of time.
  • Can Radically Reduce Testing Time: Parallel testing can divide invested time (roughly) by the number of test machines being used in parallel, so that overall testing time is a fraction of that required for sequential testing.
  • Parallel Testing Optimizes Continuous Integration and Delivery: Parallel testing in the cloud allows you to execute test suites continually as developers submit and integrate code changes throughout the day.
  • Testers Can Enjoy Cost Effective Testing: Because parallel testing is automated and can run at high concurrency in the cloud, the cost per test is considerably less.
  • It Supports Testing Science: Parallel testing enables teams to focus on making tests repeatable, measurable and accurate. Automated parallel testing delivers strong data on test results with key indicators of where tests can be improved. The net result is a test process that is more scientific.
  • The Switch to Parallel Testing is Not All At Once: The greatest advantage of parallel testing is that one can transition to parallel testing in steps, starting with the tests that are mostly easily converted to parallel, then adapting some or all of the remaining tests after the testing team has had time to adjust to the parallel testing environment.


Even though the advantages of Parallel Testing are immense, yet there are some challenges encountered by the testing team while executing this process of testing. These not only interfere with the completion of software testing, but simultaneously make the process of testing costly and time consuming. Hence, mentioned below are some of these challenges:

  • Parallel testing requires complete knowledge of the product as well as other products related to it.
  • It is vital for the team to test every outcome accurately.
  • Testers needs to concentrate on the data input and flow of product.


Parallel Testing is gaining great significance among software engineers as it conducts tests on two or more systems simultaneously. Defined by testers as a semi-automated approach of application testing, parallel testing tests applications against several environment configurations concurrently. It caters to various requirements of the client and tests the application at a reasonable price. Hence, parallel testing is the best option for organizations that want to get accurate results and ensure the effectiveness & performance of their product.

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