What is Defect in Software Testing with Example
Introduction to Software Defects
What is a defect in software testing? If you are learning software testing, you will certainly hear a lot about "defects." But what exactly is a defect? How do testers identify them? What happens after a tester reports a defect? This guide explains what a defect is and the difference between a bug and a defect, types of defects, etc., all in very simple language.
Defects in Software Testing
In Software Testing, according to International Software Testing Qualifications Board (ISTQB) a defect also called a Software Defect is an imperfection that prevents a software product or application from functioning correctly, representing a deviation from requirements, source code, test script, documentation, design or specifications or intended use.
In simple terms, a software defect means the difference between the actual result and the expected result, which is also called Variance.
Bug vs Defect: Key Differences in Software Testing
Many testers are confused about the difference between a bug and a defect, and often use the terms interchangeably.
Difference Between Bug and Defect
Both Defect and Bug terms refer to problems within a software product or application. Officially, International Software Testing Qualifications Board (ISTQB) treats both terms as the same thing, but in practice they are often used differently.
What is Defect
A Defect is when issues found by the tester during the testing process. It occurs when the actual result shows deviation and does not match with the expected result as per the given requirement.
Defect is the term mostly used by testers
Reason of Defect
- Wrong input or test data
- Environment or configuration issues
- Miscommunication between the team members
- Wrong or incomplete design
- Unclear or incorrect requirements
What is Bug
Bug is a common term used when there are issues in a software product or application. or The Informal Term.
A Bug is a flaw(mistake) in the software code that causes the program to behave incorrectly. It usually occurs due to a mistake made by the developer during coding.
Bug is mostly used by developers
Reason of Bug
- Missing Code
- Wrong Code or Incorrect Logic
- Syntax Errors
- Lack of Unit Testing or Code Review
- Misunderstanding of the requirement by developer
That is why 'Defect' and 'Bug' can be used interchangeably in real-world software development, even though teams may treat them differently.
Difference between Error, Fault and Failure in Software Engineering
Errors, faults, and failures are interconnected together, they describe where a problem originated and where and how it ultimately manifested. An error leads to a fault, and a fault leads to a failure.
What is Error in Software Testing
An Error is a human mistake in most cases, they occur because programmers and developers misunderstand requirements or make mistakes while writing code. It is the root cause of the problem.
What is Fault in Software Testing
Due to an error, it creates a fault. A fault can be an incorrect step, instruction, or piece of code, this is the actual defect or bug caused by an error. A fault remains hidden until the faulty code is executed.
What is Failure in Software Testing
A failure occurs when software does not behave as expected because faulty code has been executed. At the end, the users see the failure.
Flow: Error (The Human Mistake) → Fault (The Flaw in the Code or Wrong Code) → Failure (The Observable Breakdown or Wrong Output)
Example of Error, Fault, and Failure in Software Testing
In calculator application developer misunderstands the requirement and uses the subtraction operator (-) instead of the addition operator (+). This human error is Error. Consequently, the incorrect code such as "result = a - b" constitutes a fault. When the user enters 5 and 3, the result is 2 instead of the expected 8; this is an incorrect output and represents a failure.
Types of Defects in Software Testing
Various types of defects arise during software development that negatively impact the user experience. Distinguishing between these defects is very useful for software testers, developers, and business analysts. And the defect is assessed based on its priority and severity.
These defects are classified into the following types.
- UI/UX(User Interface / User Experienced) Defects - These types of defects affect the usability.
Example:- spelling mistakes, misaligned buttons, unreadable text, poor color combinations etc - Functional Defects - In such defects, the application does not function according to the requirements or specifications.
Example:- For instance, suppose a user wants to remove an item from their cart in ecommerce site or app, but it isn't being removed even after clicking "Remove" - Error Handling Defects - Error message not coming from wrong operation or Wrong error message is coming for wrong operation.
Example:- For instance, if you enter incorrect credentials during login, an error message should appear - Performance Defects - When software performance requirements are not met as expected.
Example:- Slow loading pages, Excessive memory consumption, High response time - Compatibility Defects - These defects occur when an application behaves differently across various environments, such as operating systems, screen size, devices, browsers.
Example:- The website layout works well in Chrome browser but looks misaligned in Safari browser - Documentation Defects - Defects are not limited to code alone, they can also exist in documentation as per International Software Testing Qualifications Board (ISTQB), requirements, specifications and test scripts.
Example:- In ecommerce site or app, 20% discount was granted in requirement document, whereas the business rule approves only 10%
There are many other types of defects also and we cannot discuss them all here are like Security defects(SQL Injection), Input domain defects(accepting letters in a phone number field), H/W related defects(application not working with a particular printer or scanner), Manipulation defects(wrong result after editing or updating a record), Data defects(duplicate customer records saved in the database), Logical defects(wrong discount calculated due to an incorrect formula) etc.
Root Causes for Software Defects and How to Overcome Them
Understanding the causes of defect in software testing is very crucial for developing reliable and high quality software. Quickly identifying these issues aids development - testing teams can prevent recurring defects, maintenance costs are reduced and the overall quality of the application improves.
Root causes of Software Bugs are as listed below.
- Unclear or Incomplete Requirements - Create clear requirement documents, confirm them with stakeholders and clients and define acceptance criteria before development begins.
- Coding Mistakes and Programming Errors - Follow coding standards, conduct code reviews, perform unit testing, identify and fix bugs early.
- Design and Architecture Issues - Conduct design reviews, follow proven architectures and evaluate maintainability and scalability before implementation.
- Poor or Insufficient Testing Practices - Create robust test cases, start testing early right from the requirements stage and conduct regular regression testing.
- Changes Introduced during Software Development - Perform impact analysis regularly, keep test cases updated and make sure to conduct regression testing after any changes.
- Poor Communication between Teams - Hold regular meetings with testers, developers, stakeholders and clients - share updates clearly, track issues and share progress using tools like JIRA.
There are also many other causes of defects in software testing that all we cannot discuss here like Lack of Training and Skills, Time Pressure and Unrealistic Deadlines, Environmental and Configuration Issues etc.
Real Life Example of a Defect in Software Testing
Consider a banking app where the requirement is that a user can transfer money to a saved beneficiary by clicking the "Transfer" button.
Test Scenario: The tester logs in using the correct credentials, selects the beneficiary, enters the amount 10000 and clicks the "Transfer" button.
Expected Result: The amount should be transferred to the saved beneficiary, and a success message should be displayed.
Actual Result: Nothing happening when click on the "Transfer" button and no message is displayed either but amout also not deducted.
Conclusion
Defects are an unavoidable part of software development, and understanding them is essential for delivering quality products. Understanding Bugs, Defects, Errors, Faults, and Failures in Software Testing helps teams communicate clearly and find the root cause quickly.
Recognizing the types of defects, such as functional, performance, compatibility, and security, helps testers report issues accurately. By identifying defects early and fixing the process behind them, teams can reduce rework and release reliable software.
Frequently Asked Questions (FAQs)
Why is it important to differentiate between Bug, Defect, Error, Fault, and Failure
It is very important to distinguish between these terms there are several reasons for this, which are listed below.
- These terms describe the various stages of a problem, its causes, and so on. Understanding these distinctions helps developers, testers, managers, and business analysts use the correct terminology, thereby ensuring clear and effective communication.
- To make troubleshooting efficient, the goal is to quickly identify the nature of the issue whether it is a bug, defect, error, fault, or failure so that the root cause can be diagnosed rapidly.
- Helping in finding the root cause (error) instead of fixing the symptom (failure).
- Helps decide who should act, clearly communicated in bug reports and team discussions.
- Recurring problems are prevented by fixing the process so that they do not happen again.
Are Faults always visible in the Software Testing
No, Faults in Software Engineering does not always remain visible it only becomes apparent when specific conditions trigger it.
What are the different types of Defects in Software Testing
It is crucial to understand the types of software defects every tester should know, as this knowledge helps in identifying, preventing and reporting defects in software applications. In day-to-day practice, testers also call these defects software errors also, so the list below covers the types of software errors in software testing as well.
UI/UX Defects, Functional Defects, Error Handling Defects, Performance Defects, Compatibility Defects, Documentation Defects, Security defects, Input domain Defects, H/W related Defects, Manipulation Defects, Data Defects, Logical Defects.
