Back to Back Testing

Software development is the process of computer programming, documenting, testing, and fixing defects and bugs, all of which is involved in creating and maintaining applications and frameworks resulting in a software product. All these stages of software development are immensely important and play an essential role in the Software Development Life Cycle (SDLC). Software Testing, which is executed throughout the development process, validates the quality of the product and ensures its performance and effectiveness.

However, software testing based on program execution may consume considerable development effort. In this context, testing of two or more functionally equivalent versions of a program against each other appeals because it offers a potentially simple way of checking the correctness of the program response to a large number of test cases. One name for this technique is Back to Back Testing, which is a cost-effective approach that is used for new software, as well as for testing software after major modifications.

Defining Back to Back Testing

Back to back testing, as defined by Somerville in 1998, is always used when several versions of software application exists for testing. Here, all versions are tested with similar set of tests and then the results are always compared for some system / application problems, if any issue exists. Back to back testing is one type of Software Testing, which is also known as Comparison Testing. It is a type of testing in which two or more variants of a component are always tested with similar input and their corresponding outputs are compared and examined, in case any discrepancies occur in the software in the future. Therefore, in back to back testing, a single test set is performed on two implemented versions of a software product and the results are compared. Whenever a mismatch occurs in the result, then one of the two versions of the components is probably evidencing failure.

Moreover, back to back testing is a process in which the events associated to it are examined and defined properly. This testing always involves cross comparison of the entire responses that are always obtained from functionality equivalent software components. During this testing, whenever a difference is determined or observed by the team of testers it is measured and if necessary it is applied too.

Example of Back to Back Testing:

A perfect example of back to back testing will be testing different versions of software that are used on the POS machines (point of sales or the card swipe machine). Here, the responses and the output is similar across all versions, with the same inputs, despite of how the data is manipulated in the backend. This perfectly reflects the features of back to back testing and validates that it is a cost-effective approach that is used by testers all over the world for new software as well as for testing software after implementing major modifications and changes in it.

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Reasons for Having Access to Multiple Implementations:

There are several reasons for testers and developers to perform numerous implementations during software development process. From client’s demand to software’s technical needs, various factors affect a tester’s decision of executing multiple implementations in a software or application. Some of these reasons are mentioned below:

  • Safety critical systems sometimes use multiple, independent implementations of critical modules to ensure the accuracy of the end result.
  • Developers or testers might use a competitor’s product, or an earlier version of their own, as the second implementation.
  • One might write a software simulation of a new chip that serves as the specification to the hardware designers. After building the chip, one could compare the results computed by the chip hardware with the results computed by the software simulator.

Process Of Back to Back Testing:

The process of back to back testing is mainly executed by a team of experienced and knowledgeable experts, who are dedicated in finding all the defects and errors in the system. This testing ensures that the various elements of all products are tested for existing discrepancies, which are then resolved to get perfect and expected results. The process of back to back testing consists of three vital stages, which are described below:

  1. Preparing Test Cases: This is the first stage of back to back testing, where specific purpose set of test cases are prepared for initiating testing on the software or application.
  2. Running the Application: Set of test cases prepared in the first stage of the testing are used here by testers to run different system or application versions. Once the tests are executed the results are stored in different files.
  3. Comparison and Reporting: This is the last stage of back to back testing in which automatic comparisons are performed of all the results stored in different files. Furthermore, a difference report is prepared, which indicates the system or application’s problems that may exist among the different system versions.

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Benefits Of Back to Back Testing:

As stated above, Back To Back testing is performed on two implemented versions of a software product, after which their results are compared for any existing discrepancies and errors. This type of testing, hence, is extremely beneficial for software engineers as well as the clients. From performing thorough comparisons to being cost effective, back to back testing is the best option for testing. Some of its major benefits are:

  • Performs comparison of two or more versions of software applications.
  • Can easily determine the perceived weakness and strengths of the software.
  • Allows one to know all the important features of the product that may require modifications or checks before its commercial release.
  • Back to back testing is a cost effective testing for new software.
  • It can perform testing after major modification and changes are implemented in the system or application.
  • Helps in understanding the design structure of the competing products, which can be used as a reliable benchmark for making future improvements and enhancements in the software or application.


There is an abundance of superior quality and technically advanced software systems and applications in the Software Industry, in today’s day and age. However, this abundance has forced organisations to develop software and applications that are unique and have exceptional features. To achieve this development goal, developers and testers all over the world are using various development and testing techniques. One such testing technique is Back to Back Testing, which allows testers to test two or more variants of a component with similar input. Once the testing is complete, the corresponding outputs of all the variants are compared and examined in case of any discrepancies that may occur in the software in the future. It is through this proper testing and comparison that one is able to find all the defects in the software and get an in-depth knowledge of the software system and application.

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