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defect leakage in software testing

What is Defect Leakage in Software Testing?

Several testing procedures and techniques find flaws throughout the Software Testing Life Cycle, abbreviated STLC. Defect leakage measures the percentage of problems that leak from one testing stage to the next, demonstrating the efficacy of testing. However, because certain defects, faults, and mistakes are present at the most internal level of the program, even the most well-known and efficient testing processes cannot locate and identify them all. 

Leakage is found in the later phases of the software testing life cycle (STLC). Proficient software engineers, therefore, use a method known as defect leakage in software testing to calculate the total number of undetected errors in software systems. This method also helps them validate their testing efforts by allowing them to determine the total number of faults present in a software program.

Defect leakage is the metric that confirms the significance of the QA testing procedure. It considers the number of problems found throughout the ongoing process. In the brief term, it is a type of defect that, when put into use, surpasses all team tests and leads to a product that instantaneously affects users.

With a compound annual growth rate (CAGR) of 6.1%, the global market for leak detection and repairs is anticipated to increase from $14.63 billion in 2021 to $15.52 billion in 2022. At a CAGR of 7.2%, the leak detection and repair market is predicted to reach $20.5 billion in 2026.

A Quick Overview of Defect Leakage

Software engineers use a method called “Defect Leakage” to determine the total extent of mistakes and flaws that go unnoticed to decide on the overall number of faults in the software application. This further helps them validate their test coverage. 

It is the ratio of faults attributable to a step but only discovered in later phases compared to the total of defects found in that step plus all defects discovered attributable to a step but only discovered in the last stages. Additional elements of defect leaking include:

  • Following the delivery of the application, it happens at the end-user or customer end.
  • They are used to calculate the defect leakage rate for subsequent.
  • It may be computed at the initial level, the overall project level, or both.
  • It is expressed as a percentage.

Testing Error in Software

A software application bug is a variance or diversion from the intended user’s needs or the initial business needs. A software bug results in inaccurate or unexpected outcomes from a software program that doesn’t adhere to the specifications as intended. While running the test cases, testers could encounter such flaws.

These two names are similar and are sometimes used indiscriminately by testing teams because both represent defects that need to be rectified in the business.

Testers can encounter test findings contrary to what was anticipated when they run the test cases. A software defect is known as this variation in test findings.

How to determine defect leakage

Defect leakage in software testing is a measurement that assesses the proportion of bugs that pass from one testing stage to the next while also demonstrating the efficacy of software testers’ testing. The value of the test team is shown only, though, when there is little to no fault leaking.

This formula is used to determine the defect leakage rate: #Defect discovered during next phase/(# Defects found during testing + #Defects found during next phase) * 100

For instance, end users found 42 faults at the UAT manufacturing unit, while 140 defects were found during the whole quality process, comprising both the testing facility and the production site. Defect leakage would thus be as follows:

= (42/140) * 100

= 30%

Therefore, 30% is the defect leakage percentage.

Maintain a record of the location of the defect and make repairs before it is released, check the development process, and keep a reasonable defect with an efficient repair.

Along with discovery and repair, software fault disclosure is also crucial. Additionally, for solutions and validation, transparency concerning software flaws is vital.

Reasons for Defect Leakage

Since software development involves several different activities, there are many possibilities as to why a defect could go unnoticed despite extensive testing. The causes of defect leaking might range from a minor mistake in the software’s coding or scripting to a lack of product or industry understanding. Therefore, a few of these causes, which might result in excessive defect leakage, are listed here.

  1. Communication issues: Defects may go undetected and unreported if there is poor or absent communication during the software development process (from requirement collection to interpretation/documentation or stage).
  2. Human error: Since people make mistakes, it would be absurd to expect the items they create to be perfect and free of flaws. That explains how software flaws and defects might appear. However, notwithstanding the probability of human-caused errors, humans still manage to produce goods that are superior to those made by any non-human entity. Therefore, we must rely on human intelligence and thus run the danger of mistakes unless we find one that can perform the task better than humans.
  3. Unachievable deployment timelines: Scarce or limited resources and due dates are among the problems that software developers frequently have to deal with. They may have to make some sacrifices as a result (such as not allocating enough time for designing and not validating their code before delivering it to the quality assurance team), which can raise the likelihood of faults and errors.
  4. Faulty design logic: Finding a dependable solution requires both R&D and some level of conceptualizing as software applications become complex. However, a strong desire to do the project quickly, lousy use of expertise (i.e., products, components, processes), and poor knowledge of technological viability before creating the architecture are all factors that might cause errors or bugs to appear.
  5. Poor coding: This includes bad coding techniques like unhandled failures, missing deviations, and incorrect input validations, as well as the use of inadequate tools (like poor compilers, debugging tools, and validators that some software developers are using). All of these can introduce bugs in the code that may be difficult to troubleshoot. Sometimes, problems in the code may be the result of poor programming.
  6. Not using version control: Examine the version monitoring system (if there is one). If the tester experiences frequent regression errors, trace every change made to a collection of code bases using parallel version systems.
  7. Defects in third-party tools: During software creation, third-party tools like debuggers, HTML builders, shared DLLs, and add-ons/plug-ins (such as shopping cart connectors and map navigator APIs) are frequently required. However, these third-party tools may have defects that get transferred to the product.
  8. Lack of experienced testing: Subpar testing is frequently the norm in many companies. This could involve a shortage of skilled testers, flaws in the testing procedure, testing treated carelessly, and the method is carried out without consideration. All of these have the potential to lead to software flaws and failures.
  9. Excessive reliance on automation testing could result in a manual tester missing a bug or fault since automated testing lacks human perception and experience.

Strategies to Control Defect Leakage

Software engineers are engaged in an ongoing conflict that will never be ultimately won. Defects do occur. As a result of deadlines or constraints, software engineers may even intentionally add flaws to their products. However, how can unwanted vulnerabilities that make the application challenging to use and damage reputation be fixed?

As the project’s relevance rises, more effort should be spent managing production-site issues. Defects may be significantly reduced by using sound test recording, reporting, customer interaction, and product openness. Even the most significant log in the world is partly useless if the flaws are not corrected.

Program developers and testers must employ several approaches to avoid defect leakage, guarantee that it is managed and does not remain in the software, and certify the quality of the finished output. This reduces their overall engineering and testing resources and enables them to prevent any significant problems during the software development cycle. So, the following are some methods to stop excessive defect leakage in software testing:

  • Pick a locus, then do extensive testing and analysis.
  • Create a simple, concise report that may be utilized in interactions with and among the business and corporate leadership to assess the general health of a quest application quickly.
  • Automatically record production-related flaws. This method might get complicated very fast, so have a separate area to document faults and add pertinent concerns.
  • Set up a small SWAT squad or fast reaction team that can respond rapidly to crises if the group is large enough or the project is vital enough.
  • Additionally, as a general rule, each developer should be attentive to the state of their product, actively involved, and accountable for their code.
  • Look for components susceptible to significant defect leakage and critical content and locations.
  • Test the product thoroughly on the minor components before using a real-world simulation.
  • If issues are terrible, think about rewriting them and look more closely at the entire system.

A suitable fault extraction efficiency and maintaining track of problems discovered and fixed before release are indicators of healthy software development. Keeping track of any issues found after deployment and reporting them to the product, engineering, and quality teams are vital so that test cases can be upgraded and procedures may be changed as needed. Since most consumers want to understand taking responsibility for the issues and striving to find solutions, visibility concerning software errors is just as crucial as discovery and correction.

Steps to fix the defects:

Software engineers and QA testers can resolve the issues by following the instructions below.

  • Assign to someone: The task is delegated to a developer or specialist, and the status is changed to responding.
  • Setting the schedule: This step is handled by the development side. They will design a timeline to resolve these issues depending on the fault priority.
  • Repair the bug: While the project team resolves the flaws, the Testing Team monitors the procedure and compares it to the timetable.
  • Submit the solution: When bugs are fixed, request a resolution report from the developers.

Validation :

The testing team confirms that the flaws are rectified after the design team fixes and documents the problem.

For instance, in the situation above, once the development team reports they have addressed 71 flaws, the team needs to retest to see whether these bugs have been resolved. 

A defect is converted to closed status after it has been fixed and validated. If not, then the team notify devs to recheck the fault and consider the following:

  • Appropriately calculate the defect percentage.
  • Calculate the overall project and phase levels.
  • Openness for the product.
  • Reliable test logging.
  • Include engagement from the client.


Although finding bugs and defects is essential for software’s correct and efficient development, doing so at a crucial time or in large quantities can have fatal results. Software testers and the Quality Assurance (QA) team are responsible for swiftly detecting any flaws, errors, bugs, and other problems in a system. Doing so will allow them to produce successful software or applications with high standards for quality, performance, functionality, and other aspects. Defect leakage testing is straightforward, thanks to Testsigma’s intuitive interface.

Since everything is already configured, the initial setup requires little time or effort. You can do defect leakage testing quickly and maintain automated tests quickly with Testsigma. The best method for evaluating test coverage is defect leakage. They may also calculate the percentage of flaws that leak to a later stage and obtain the total number of concealed and unrecoverable faults with the help of the matrix defect leakage. Furthermore, defect leakage is significant since software testing is more effective when defect leaking is minimal.

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