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Negative Testing in Software Engineering

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Every software development process follows Software Development Life Cycle(SDLC) finally to develop a quality software product. Software testing is one of the important phases as it only ensures the quality of the product. So, for that different types of software testing are performed to check different parameters or test cases. Negative testing is a type of software testing that focuses on checking the software application for unexpected input data and conditions. The article focuses on discussing Negative Testing in detail. 

What is Negative Testing?

Negative Testing is performed to ensure that the software application or the product does not fail or behave abnormally whenever a user gives any unintentional or unexpected input to the software application. The purpose of negative testing is to check how the software behaves when some unexpected input is given to the software. This testing is performed to break the system and verify the response of the application during unwanted inputs.

  • In negative testing, the system is authorized to provide invalid data as input.
  • It makes sure that the product does not fail when an unpredicted input is given.
  • It is also known as failure testing or error path testing.
  • It spots the negative characteristics of the application by designing test cases.

Characteristics of Negative Testing

Below are some of the characteristics of negative testing:

  • Evaluate security breaks: It helps to evaluate potential security breaks and special handling procedures.
  • Display data corruption: Negative testing helps to display security violations and data corruption.
  • Identify defects: Negative testing is performed to identify defects that if undetected can result in essential breakdowns.
  • Uncover software vulnerability: It helps to uncover the software vulnerabilities and potential for exploitation.
  • Stability of application: It helps to guarantee the stability of the application after being come across the input values, outside the limit or scope.
  • Finds loopholes: Negative testing helps to find the critical loopholes and weak areas resulting in its failure.

Purpose of Negative Testing

  • Validate application for unexpected inputs: The main objective of negative testing is to validate the application response throughout the unexpected inputs.
  • Ensure application constancy: Negative testing helps to ensure the constancy of the application against the impact of different variations of the invalid data set.
  • Enhance application quality: Negative testing is done after positive testing and helps to identify bugs and enhance the quality of the application.
  • Enhance software performance: Negative testing helps to ensure ideal software performance even when the user enters invalid data.

Need for Negative Testing

  • Deliver bug-free products: Negative testing helps to make sure to deliver bug-free products and products with zero vulnerability to meet customers’ expectations.
  • Deliver good quality product: The organization needs to perform negative testing needs to be done to deliver a good quality product to the customer.
  • Ensure that failure is avoided: It’s not always possible to guarantee a 100% bug-free product, but it is important to ensure that everything is done to avoid failure.
  • Crucial Applications: Negative testing is important for crucial applications like online stock, e-commerce, etc.

Why do Testers avoid Negative Testing?

  • Cause unnecessary delay: A lot of testers avoid performing negative testing as they think that it may unnecessarily cause a delay in the launch of the product.
  • Waste time and resources: Some testers consider negative testing as a distraction that wastes time and resources and they consider it to better spend time and energy performing positive testing.
  • Lack of skills: The lack of skills and knowledge also hinders testers from employing negative testing. 

Techniques to Perform Negative Testing

Below are some of the techniques that can be used to perform negative testing:

  • Boundary Value Analysis: BVA involves writing test cases for the values that are outside the boundary limits.
  • Equivalence Partitioning: This technique involves grouping the input values into various partitions and testing some values in every partition.
  • Error Guessing: This technique is used to pinpoint the specific conditions that trigger failure or error messages.
  • Checklists: This involves documenting the error conditions that one is planning to test and it is used in tandem with error guessing.
  • Anti-patterns: These are the ideal source of negative tests and these are antithesis.
  • Fuzz Testing: This technique involves inputting random data which may cause unexpected failures and there are no preset expected results.
  • Exploratory Testing: This technique can be carried out simultaneously with the other tests and is used to increase knowledge about the application and to show which aspects of the application work and what does not.
  • State Transition Testing: This technique is used to spot defects in the application. A program is considered in its normal state until an issue reveals itself.

Examples of Negative Testing

Below are some examples of negative test cases:

  • Login page: Blank user ID with a blank password, correct user ID with an incorrect password, incorrect user ID with an incorrect password, incorrect user ID with the correct password, and so on.
  • Uploading images: Uploading image files of size out of permissible size limits, uploading image files with an invalid image file type.
  • Uploading documents: Uploading documents with invalid file types. For example, if only pdf is allowed and a .docx file is being uploaded. 
  • Navigations in the application: Tester may test the invalid navigation route in the application that is different from the standard path. 

Negative Test Cases

Some components of Negative testing are called Negative test cases. The team creates it to test the application. The team uses the following testing efforts:

  • Data Bound Test: The team tests all the upper and lower bounds of data fields.
  • Correspondence between data and field types: The team tests how the application reacts when wrong data is entered into a control.
  • Field Size Test: It prevents users from facing more characters before getting the error message that they have crossed the limit.
  • Necessary Data Test: The test ensures that every data on the screen is verified before critical data is entered.
  • Numeric Bound Test: This test ensures that test cases of the negative tests are accurate where the team analyzes both lower and upper bounds.
  • Implanted Quote: Software systems face some issues when end-users store information with a single quote. So for all the screens, the team should provide more than one single quote.
  • Modification in Performance: This test contains test cases that compare previous and current release performance statistics which can help to identify potential performance problems.
  • Web Session Testing: The testing team builds test cases to release web pages within the application only which don’t involve user login.

How to Perform Negative Testing?

  • Consider all possible cases: Initially it is important to think about the possible scenarios that could affect your application negatively.
  • Prioritize the inputs: While exploring scenarios we need to prioritize some testing parameters where it is ensured there is no waste of time or money.
  • Design test cases: Now we build a test case that includes testing of data input where the application may be crashed. That is exactly what we don’t want to happen when a client uses the product.
  • Eliminate security pitfalls: The security pitfalls should be eradicated while forming priorities of the test cases.

Benefits of Negative Testing

  • Helps identify incorrect bug processing: Negative testing helps to confirm if the software code stopped managing a programmed use case, thus avoiding application failures caused by faulty bug processing.
  • Covers all aspects: It covers all bases and enhances the possibility by covering each type of error. To ensure all test cases are covered, one round of negative tests is performed before positive testing.
  • Ensures good quality product: Implementation of negative testing ensures a product is of good quality with zero or negligible vulnerabilities.
  • Helps to maintain a clean database: Negative testing increases the possibility that only valid information is stored and displayed by the application and thus the database will be in good condition as it will contain only valid data. 

Limitations of Negative Testing

  • Adds to cost: The execution of it requires an investment of time, money, and effort.
  • Extreme delays: Customers have extreme delays as they have to wait till the product is released.
  • Sometimes unnecessary: In some cases, there is no need to execute excessive negative testing.
  • Skilled professional required: There has to be a trained and professional engineer in order to implement Negative testing.

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Last Updated : 17 Aug, 2023
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