What is a Defect or Bug?

What is a Defect or Bug?

What is a Defect or Bug?

A defect or bug is flaw in any software system that can cause the software system to fail to perform what its actually supposed to perform. A defect gets introduced in software work product due to the mistake made by the person creating that software work product like software requirements, design documents (High Level Design/Detailed Design), Test Plan, Test Scripts, Software Code etc.

What is a Defect or Bug?
What is a Defect or Bug?

While testing when a tester executes the test cases, he might observe that the actual test results do not match from the expected results. The variation in the expected and actual results is known as incident which will require investigation.

Every incident that occurs during testing may not be a defect or bug. An incident is any situation in which the software system has a questionable behavior, however we call the incident a defect or bug only if the Root Cause is the problem in the tested component and not other factors like test environment/test scripting issues.

Incidents can also occur by some other factors as well like testers mistake in test setup, environment error, invalid expected results etc.

We log these incidents just to keep track of the record of what is observed during the testing so that we can find out the solution to correct it.

A defect can be introduced in any phase of SLDC(Software Development Life Cycle) so it is very important that test team is involved from beginning of SDLC for detecting and removal of defects. The earliest the defect is detected and rectified, the minimal cost of quality will incur.

For Example: If the defect is identified in requirements phase then the cost of fixing it is just modifying the requirement whereas if the wrong requirement is designed and implemented in the code and found during the test execution phase then the cost to fix that defect will be very high as the fix needs to be done in requirement and then those changes need to propagate to design, development and testing again.

Types Of Defects

Defects are classified based on the specific part of the software product they affect, the priority of their resolution, and their severity. Let’s take a closer look at all three classifications.

Software Defects Depending On The Aspect They Affect:

Integration defect:

An issue when using a digital solution due to incorrect interaction between multiple program modules. Integration testing helps identify and resolve these defects.

Performance defect:

A defect that affects the quality of the software product’s performance, such as processing speed, efficient use of resources, etc. The testing team must conduct thorough performance testing to detect deviations from specified performance requirements.

Logical defect:

A software malfunction that results in incorrect request processing results or any other unexpected behavior of the digital solution. To identify such defects, it is recommended to use debugging tools for step-by-step code checking.

Functional defect:

An error that affects the correct execution of the software solution’s functions. Functional testing helps resolve such issues.

Usability defect:

An error directly affecting the user experience, making working with the app inconvenient and challenging. Usability testing is necessary to identify and address these errors, as it ensures the digital product aligns with user requirements.

Security defect:

An issue that can allow cyber criminals to access users’ confidential information. Such defects are critical and require strict control and immediate resolution. Security testing helps address these concerns.

Compatibility defect:

An error that leads to incompatibility between multiple software products that should interact or between apps and hardware. They can be resolved by performing compatibility testing.

Syntax defect:

An issue that arises from inaccuracies in the code, typically resulting from a developer violating the programming language’s rules. Syntax defects are usually easy to detect since the app fails to launch when they are present.

Defects Of Software Products By Severity:

Critical: have catastrophic consequences for the functioning of the software.

Major: significantly impact the functionality and performance of the software program.

Minor: have a negligible impact on the app’s performance, such as causing it to run slower.

Trivial: do not affect the software product’s functioning or the user experience’s quality.

Depending On How Serious A Defect Is, The Testing Team Assigns It A Certain Priority Level:


Other Software Defects Do Not Fall Into Any Of The Classifications Above. They Include:

Specific product requirements not included in original product requirements lead to missing defects.

Wrong Defects arise from a mismatch between the product requirements and user expectations, usually due to their incorrect formulation.

Regression Defects manifest as disruptions in the functioning of another module due to code changes made in a specific part of the system. Regression testing is conducted to detect such defects.