What is Negative Testing? With Test Case Example

What is Negative Testing?

Negative testing, a vital form of software testing, examines how an application handles unexpected input data and test scenarios. Testers intentionally use random, incorrect, and even strong hacking attacks to assess the application's resilience against potential bugs and errors. By subjecting the software to unexpected conditions, negative testing ensures that it adheres to requirements and functions reliably in real-world scenarios.

The main purpose of negative testing is to analyze the behavior of the software application by exposing it to invalid inputs. This is done to prevent the software application from crashing due to negative inputs and improvise its quality and stability. However, by performing positive testing, testers can only ensure that the application works adequately in normal scenarios. It is equally important to ensure that the software application handles unexpected conditions to ensure that it is completely bug and error-free.

Negative testing serves several important objectives for software developers and testers. Here are some of those as follows:

• It functions as a crucial part of the software quality assurance that helps testers to verify and validate the performance of the software application as expected and aligns with the customer's requirement.
• It checks the functionality of the software application when faced with invalid inputs. It intends to provide a better user experience by minimizing the chances of user frustration or system failure.
• Identifies and addresses stability issues that may remain unnoticed during positive testing.

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Importance of Negative Testing in SDLC

Negative testing holds significant value within the Software Development Life Cycle (SDLC) as it plays a pivotal role in ensuring the software's excellence and security for its intended purpose. Below, you'll find simplified explanations highlighting the importance of negative testing in the SDLC:

• When running negative tests, detection of any bug or error in the software application during the early stage of SDLC can be done. It helps improve the software application's quality and functionality by lowering the risk of defects and errors.
• In SDLC, analysis of the Software Requirement Specification is very crucial. Here, negative tests validate this and ensure that software applications perform as per specification, and that invalid inputs are handled correctly.
• By testing how the software product performs under adverse conditions, we can demonstrate its ability to function correctly even when things go wrong. This builds trust in the software's reliability and boosts the user's confidence.
• The common risk associated with software applications, like the risk of loss or corruption of data, can be eliminated. This, in turn, ensures that the developed software application meets the requirement of the end users.

Benefits of Negative Testing

Negative testing, also known as "fault injection" or "error path testing," holds profound importance in software development. It encompasses the detailed test of a software application's behavior when subjected to unforeseen circumstances.

While positive testing ensures the software application's proper functioning under normal conditions, negative testing exposes vulnerabilities, weaknesses, and potential points of failure. Let's understand the benefits of negative testing from the organization and customer perspectives.

Perspective from Organizations:

• Delivering a top-notch application: Organizations are responsible for providing dependable and resilient software applications to their customers. Negative testing plays a key role in identifying potential failures and weaknesses, enabling organizations to enhance the overall quality of their software applications.
• Validation against failures: It validates the software application's capacity to handle failures, errors, or exceptions gracefully. By intentionally injecting issues, organizations can evaluate the system's resilience and ensure it responds appropriately in such scenarios.
• Failure prevention: It is very challenging to develop 100% error- and bug-free software applications. However, ensuring the software application does not fail after being released in the market is equally important. For this, negative testing is needed to mitigate the risk and identify any points of failure.
• Security consideration: Negative testing is required to uncover any security vulnerabilities in the software application. Its execution is needed as it mimics the attacks to detect security-related issues like SQL injection to protect sensitive data.

Perspective from Customers:

• Expectation of resilience: The common expectation that every end-user has for the software application is its high quality and stability. With negative testing, it is easy to ensure that any vulnerabilities and bugs can be identified and fixed, giving robust software products to end users.
• Cost considerations: While negative testing involves additional time, effort, and resources, its benefits outweigh the costs of developing software applications. It considers mitigating any potential software application failure and thus lowers future costs.

Disadvantages of Negative Testing

Like other software testing types, negative testing is no exception and has some disadvantages. Some of those explained:

• In software engineering, it can be unnecessary in certain cases, such as when unlikely scenarios or conditions are considered. Evaluating the relevance of negative tests is crucial to optimize testing efforts efficiently.
• It is time-consuming and needs extensive testing of edge cases and invalid inputs.
• The major challenge encountered in negative tests is automating the process. It is due to creating test cases that correctly represent invalid inputs and the ability to interpret the result.
• The management of invalid inputs may require additional hardware and software. Hence, we can say that negative tests can be a resource-intensive process.

Example of Negative Testing

Consider the scenario of testing the login functionality of a website. To exemplify negative testing, let's focus on boundary value testing. Suppose the system stipulates that passwords must consist of a minimum of 8 characters and a maximum of 16 characters.

In this case, you would test the software application by entering passwords that precisely adhere to the 8-character limit, passwords that exceed the 16-character limit, and even passwords that contain the minimum or maximum allowable characters minus one. It's like entering a password with one less character than required or allowed.

Doing this lets you check how the software application handles these extreme cases. For example, does it allow too short or too long passwords? Does it display the appropriate error message? Negative testing helps you identify flaws in the software application's password validation mechanism and ensures that it behaves correctly when faced with invalid input.

This type of testing serves the crucial purpose of preventing users from breaching the software application's security measures by entering passwords that fail to meet the specified requirements. The significance lies in its ability to fortify the software application, enabling it to navigate diverse scenarios and effectively preempt any potential security vulnerabilities.

Thus, negative testing, in this particular instance, plays a pivotal role in validating the functionality of the login system, even in the face of invalid inputs, such as passwords that fall outside the acceptable length range.

Types of Negative Testing

Different types of negative testing are implemented by software developers and testers to assess the performance of the software application in different scenarios. Some of those are as follows:

Boundary Value Testing

One effective approach to testing software applications involves subjecting them to inputs located at the extreme limits of the input values. By evaluating these exceptional values, potential underlying issues within the application can be easily uncovered, particularly at the boundaries of acceptable inputs.

Input Validation Testing

Another form of negative testing entails examining the software application's capacity to handle invalid inputs, encompassing invalid data types, out-of-range values, and even the presence of invalid characters. Consequently, this form of testing enables a comprehensive assessment of the application's ability to reject and identify the inputs.

Exception Testing

While assessing software applications, exception testing is crucial. This type of negative testing focuses on examining the application's capability to effectively handle extraordinary conditions, including scenarios such as missing data, unexpected shutdowns, and other exceptional events.

Load Testing

To ensure seamless functionality, software applications are subjected to load testing. Such tests are designed to gauge the application's performance under heavy usage and stressful conditions, such as high traffic volumes, extensive data processing, and other resource-intensive scenarios. Conducting load testing can quickly identify and address potential system failures or performance issues.

Compatibility Testing

When performing comprehensive testing, compatibility testing takes center stage. This particular form of negative testing meticulously examines the software application's compatibility with diverse hardware, network configurations, and software setups. Through this examination, developers can ensure that the application seamlessly operates across various environments, safeguarding against potential compatibility issues.

Now that you have become familiar with the different types of negative testing, let's look at how to set up testing environments to run negative tests.

Test Environment Setup for Negative Testing

Getting started with negative testing requires some preparation to ensure a hassle-free test execution. One of the most important aspects of initiating the negative test is setting up a test environment. It is defined as configuring the required infrastructure, tools, and resources to have a controlled environment for testing the software applications. Here, the following components are involved in the test environment setup for a negative test:

Test Environment Requirement

When you perform a negative test, certain requirements must be aligned with the test process.

When running the negative test, you need to have the necessary hardware components and software configurations which support the software applications to be tested. This will also help to mimic real-world conditions and negative test scenarios.

For example, if you perform a negative web application test, the test environment involves having a database, operating system, browsers, and a particular version of web servers. You may also need network configurations like firewalls, proxies, and load balancers. Hence, the test environment should be similar to the production environment for accurate testing.

Test Data Preparation

It is one of the crucial aspects of a negative test that includes identifying and creating test data with invalid and unexpected input values. Its main objective is to verify and check the functioning of the software application and how it handles such inputs. For example, it verifies how it responds to the inputs by returning error messages and appropriately handling the exceptional test scenario.

Test Tools and Frameworks

In negative testing, automation testing frameworks or tools play a crucial role as it automates the complete test process. When using the manual approach for negative testing, executing the negative test cases is challenging due to the involvement of a huge amount of time and test efforts.

Further, it is also prone to error which might not represent the performance of software applications in unexpected test scenarios. Hence, using automation tools and frameworks is preferred for the execution of negative test cases, capturing test results, and facilitating test management.

Some tools used and frameworks for negative testing include the following:

• Test management tools: These types of tools are used by developers and testers for organizing and managing test cases, test execution cycles, and test data. You can track defects and report issues while performing testing. Some of the test management tools include TestRail and qTest.
• Test automation tools: These tools are used for automating the test cases, which helps in the seamless execution of negative tests and enables repeated testing. They are also helpful in simulating negative scenarios and generating test data. Some commonly used test automation tools are as follows:
• TestMu AI: It is a cloud-based digital experience testing platform that allows access to over 3000+ browsers, versions, and OS. It offers various testing capabilities like parallel testing, real-time testing, and real device cloud testing. It integrates with various automation tools like Selenium, Cypress, Playwright, which allow the testing of software applications across different environments.

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  You can simultaneously execute negative tests on different browsers, operating systems, and devices. This feature ensures broad test coverage and reliable test execution. It offers visual regression testing capabilities, using which you can capture screenshots and compare the expected and actual outputs and outcomes. Hence, you can easily identify visual defects arising from negative scenarios.

• Selenium: It is one of the most used open-source automation testing frameworks for web applications. Selenium supports multiple programming languages like Java, JavaScript, Python, and others. With Selenium, you can execute tests across multiple web browsers.

  It provides various methods and commands for interacting with web elements. This allows you to simulate different negative inputs and helps in reliable interaction with the elements.

• Cypress: It is a JavaScript-based end-to-end testing framework, particularly for web applications. It offers a live reloading feature to see the changes to the test scripts and code in the test runner in real time.

  Cypress helps you to pause and debug test execution at any time during the process of a negative test. This feature helps identify errors and evaluate software applications' function during negative test scenarios.

• Mocking and Stubbing tools: These tools help mimic specific behaviors of dependent software applications or their components that are unavailable or difficult to replicate in the test environment. Some of the mocking and stubbing tools include Mockito and WireMock.

Negative Testing Scenarios

While running the negative test, having a test scenario is essential to pinpoint possible failure of the software application in different situations. Here are some potential scenarios where software applications can unexpectedly encounter errors and crashes.

• Populating required fields

  Many software applications and web pages have fields the user must fill out. In this scenario, a negative test would involve leaving the required fields blank to evaluate how the software application responds to this situation. The expectation is that the application should provide appropriate error messages or prevent submission until all required fields are filled.

• Correspondence between data and field types

  Digital forms and dialog boxes typically expect specific data types, such as text, numbers, dates, or times. A negative test in this scenario would involve entering data of the wrong type into a field to observe how the application reacts. The application should ideally detect and handle incompatible data types gracefully, such as displaying an error message or rejecting the input.

• Allowed data bounds and limits

  Some applications have input fields with specific ranges or limits for data entry, whether numbers or text. Negative tests here involve inputting values that exceed or fall outside the specified boundaries of a field. The application should appropriately handle such inputs, such as rejecting out-of-range values or displaying warnings.

• Allowed number of characters

  Certain software applications restrict the number of characters that can be entered in a field. Negative testing would involve entering more characters than the field allows and testing whether the application enforces the character limit correctly by truncating or rejecting the extra input.

• Web session testing

  Some web browsers require users to log in before accessing certain web pages. Negative testing in this scenario would involve attempting to open web pages within the application without logging in first. The expectation is that the application should recognize the absence of a valid session and prompt the user to log in before granting access.

• Reasonable data

  Some software applications have fields that expect input within a reasonable range or format. Negative tests involve inputting invalid or nonsensical data into these fields to see how the application handles it. The application should ideally detect and reject invalid data, providing appropriate error messages or preventing further processing.

  When performing negative testing, it is essential to design well-crafted test cases that align with the specific type of testing being conducted. These test cases should be carefully created to simulate real-world scenarios and assess the application behavior, robustness, and compliance with software requirements specifications.

Designing Negative Test Cases

In performing negative tests, designing test cases is a crucial step. This involves identifying test scenarios where the software application should work or function as expected. It tests the software application with incorrect inputs to accurately verify how it handles those scenarios.

Here are the key steps to designing negative test cases:

• Identify potential negative scenarios

  It is the first step in designing test cases, which involves reviewing the Software Requirements Specification (SRS), use cases, and functionalities to identify potential negative scenarios. These steps led to finding the scenario where the software application may fail or give unexpected results. That scenario might include error conditions, boundary cases, and situations.

• Determine the expected outcome

  For each negative scenario, determine what the expected outcome should be. This involves understanding how the system should handle invalid inputs or unexpected conditions. The expected outcome could be an error message, system crash, efficient recovery, or predefined behavior.

• Choose the input

  When an expected outcome is determined, choose the inputs that cause the software applications' negative behavior. This input may not typically be encountered during normal usage.

• Design the test cases

  Based on the collected information, create test cases by detailing the steps to be executed during the negative test. Here, the negative test cases include specific inputs, the underlying activities to be performed, and the expected outcome. While creating test cases, always document the valid conditions of test cases and exhibition of the behavior of software applications.

• Execute test cases

  When the test case is designed, now its execution can be done on the software application under the test. Here, a comparison of the actual and expected outcomes is required to determine whether the software application functions correctly in negative scenarios.

Have you thought about the defects that we get while running negative tests? These defects must be effectively managed and fixed for the success of the software applications. Let us understand this in detail.

Managing Defects in Negative Testing

The defect management identified in negative tests involves different steps and procedures that effectively handle defects identified during the test process. It covers an entire defect life cycle, from discovery to resolution and closure.

Defect Management Process

This process entails various essential activities, which are as follows:

• Defect logging: The defects identified are logged in the centralized system for effective tracking and management. Here, the system captures correct information like details of defects and their severity and priority.
• Defect triage: The identified logged defects are then reviewed by the team and prioritized based on their impact, urgency, and severity. In this process, the allocation of resources is done, and the testers evaluate each defect to find a way of addressing those.
• Defect assignment: After reviewing the defect logged, it is assigned to the development team for its early fixes.
• Defect resolution: In this process, the development team evaluates the defects and identifies their root causes. Later, they implement code fixes and changes to fix the defects.
• Defect verification: When the defects are fixed, retesting is performed by the QA engineers to verify the functionality of the software application.
• Defect closure: Once the verified fixes are deemed satisfactory, the defects are marked as closed in the defect tracking system. This closure signifies that the reported issues have been adequately addressed and resolved.

Classification and Prioritization of Defects

Effectively classifying and prioritizing defects are crucial for efficient management. Defects are typically classified based on their severity and impact on the application under test, enabling a prioritization strategy that ensures immediate attention is given to critical issues.

• Critical defects: These defects cause the system to crash, fail, or corrupt data. They demand immediate attention and are typically assigned the highest priority.
• Cosmetic defects: They are aesthetic or cosmetic, such as UI alignment issues or typos. While they do not affect functionality, addressing these defects is important for a seamless user experience.
• Minor defects: These types of defects have a lower effect on the software application's functionality and performance. Even though they are not very critical, but need to be addressed to ensure the quality of the software application.
• Major defects: These types of defects have a larger impact on the software application's functionality and performance. Thus, these defects have to be addressed without any delay.

By effectively classifying and prioritizing defects, development and testing teams can focus their efforts on resolving the most critical issues promptly, ensuring that the defects with the highest impact are addressed first.

Root Cause Analysis

It is a systematic identification and analysis of the cause of defects identified during the negative testing of software applications. In other words, the tester executes root cause analysis to find the reason behind the defects for the implemented invalid inputs and negative test cases. There are different approaches used for the execution of root cause analysis. Some of those are the 5 Whys and Pareto analysis.

• 5 Whys - repeatedly asking "why" until the root cause of a defect surfaces. It suits issues that do not need advanced statistical analysis.
• Pareto analysis - a bar and line chart that ranks defects by frequency or cost, so teams fix the small number of causes behind most failures first.

Together, the defect management process, classification and prioritization, and root cause analysis keep defects from negative tests tracked and resolved. Next, let us look at the techniques used to perform negative testing.

Techniques Used for Negative Testing

Negative testing plays a key role in software testing, validating the system's behavior when encountering unexpected or invalid inputs. This form of testing is essential in identifying potential vulnerabilities, weaknesses, and defects within the software application. Diverse techniques are employed to execute effective negative testing, including:

• Boundary value analysis: This technique involves testing input parameter boundaries or extreme values. Its objective is to ascertain whether the system behaves correctly at the lower and upper limits while verifying the handling of values just within and outside those limits.
• Equivalence partitioning: It subdivides the input sections into distinct equivalence classes or groups expected to exhibit similar behavior. Its purpose is to ensure that test cases are chosen from each partition to validate the system's response for each class.
• Error guessing: This technique is informal and relies on the tester's experience and intuition to identify potential error-prone areas in the software product. Test cases are devised based on well-informed speculations about areas where defects are likely to arise.
• Checklists: Checklists provide a structured approach to negative tests by outlining potential error scenarios, test conditions, and test cases. They remind testers to cover various aspects and help ensure comprehensive testing.
• Anti-patterns: Anti-patterns are simple designs that seem appropriate; however, they lead to cause execution practices that carry software defects. These patterns need to be recognized and tested to make your system defect free. Removal of anti-patterns will also make your system robust.
• Exploratory testing: Exploratory testing can be performed by designing and executing the test cases simultaneously. In this technique, the testers interact with the software applications by providing various inputs and test cases to find defects. Exploratory testing is used when there is a chance of defects being unfounded by executing the pre-designed test cases.
• Small-scale test automation: Small-scale test automation allows testers to test, test cases that are repetitive or involve complex combinations of input using the automation testing tool. This helps by saving time and effort. Further, the saved time can be used for performing ad hoc or exploratory testing.
• State transition testing: The technique of state transition testing can detect any type of defect in the software application. The principle involved in this testing process is that the software application changes its state with every change in input. This means that state transition testing detects the behavior of the software application with the change in inputs.
• Cause-effect graphing: Cause-effect graphing is a technique that generates a graphical representation of inputs and their corresponding outputs or effects. It assists in identifying test cases that cover all possible combinations of inputs, thus ensuring comprehensive testing.
• Risk-based testing: Risk-based testing prioritizes test efforts based on the impact and likelihood of potential defects. It focuses on high-risk areas, such as critical functionality or complex modules, to ensure effective testing.
• Negative test case documentation: Negative test case documentation involves creating a repository of test cases specifically designed to assess the system's behavior under negative scenarios. These test cases document the expected outcomes and aid in tracking testing progress.
• Fuzz testing: In this technique, the software application is provided with the input of random data, leading to unexpected failure and issues. In such a situation, unlike other negative test cases, there is no preset expected outcome. Testers execute fuzz testing to observe potential occurrences due to arbitrary inputs.
• Penetration testing: This technique is based on ensuring the security of the software application. It mimics real-world attacks and security vulnerabilities to detect any security loophole in the system and analyze its ability to overcome or withstand those.
• Static code analysis: This testing technique does not involve the execution of source code to test the software application. It helps identify coding errors, security vulnerabilities, and others to uncover issues that might cause the occurrence of negative scenarios.
• Error injection techniques: Error injection techniques deliberately introduce errors or faults into the system to observe how it responds. Examples include injecting network errors, memory leaks, or invalid data.

How to Perform Negative Testing?

To run a negative test, consideration of all negative test cases is essential. If you are performing a negative test, you must consider every test case without considering the right way to use it. Let us explain this with an example. When you encounter an email field, it is essential to think and test various inputs that users might enter apart from the expected email format.

Below are the standard steps to be followed for performing a negative test:

• First, you have to review and evaluate the designed negative test cases. It is a crucial step as you can ensure that test cases include invalid inputs, test scenarios associated with security vulnerabilities, and other potential issues.
• In the next step, you have to generate invalid inputs for testing software applications. For this, you can use manual or automation tools. However, using automation testing tools is preferred because it simulates a wide range of negative test scenarios that would otherwise be difficult to replicate manually.
• Observe and monitor the behavior of the software application once the negative tests have been executed. You must pay close attention to any unexpected or undesired outcomes, errors, crashes, or vulnerabilities that may arise during the testing process.
• After the execution of the negative test, you have to analyze the result to detect any bugs or issues uncovered in the previous test. This will give you information on the performance and behavior of the software application by subjecting it to negative scenarios. Based on this, you can fix defects, enhance error messages, strengthen error-handling mechanisms, or implement additional security measures.
• You have to repeat the process multiple times by changing the test cases and input. Followed to this, you have to document the result of negative tests.

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Difference Between Positive and Negative Testing

Challenges in Negative Testing

Tackling challenges that arise during negative testing requires thorough preparation. Here are some key obstacles we have identified:

• Identifying all possible negative scenarios and edge cases for testing can pose a significant challenge. It necessitates meticulous consideration to ensure comprehensive coverage.
• Generating realistic and meaningful invalid inputs can be an issue, requiring an in-depth understanding of the system and its behavior under adverse conditions.
• Testing time-sensitive scenarios, such as timeouts or race conditions, presents particular difficulties. Specialized tools and techniques might be necessary to address these challenges effectively.
• Managing the test data employed in negative tests can be problematic, often involving generating and maintaining substantial amounts of data.

To overcome these challenges, meticulous planning, deep system understanding, and appropriate resources are essential.

Best Practices for Negative Testing

To minimize the negative impact of the tests and overcome the above challenges, you have to implement some best practices for negative testing. Here are some of those:

• Prepare a strategy for your negative test approach by accurately planning the negative test scenarios and inputs to be tested.
• Automate the negative testing procedure whenever feasible to enhance efficiency and minimize the potential for human error.
• For all your testing efforts, you should clearly define the related goal and objectives. Along with this, you should address this by executing the negative test.
• Always test the edge cases and boundary conditions of the software application by prioritizing it because they are prone to encounter invalid inputs.
• Whenever possible, use real-world data to generate invalid inputs to represent the users accurately.

Conclusion

Negative testing is important as it knowingly tests the software application with invalid inputs and unexpected scenarios. By performing negative test cases, vulnerabilities, defects, and weaknesses can be determined and addressed before affecting end-users.

Thorough planning, test case design, and understanding of the software application's performance and working are key for effective testing. Embracing emerging technologies, integrating with DevOps and Agile development practices, and adopting predictive and AI-driven approaches enhance the process. Hence, negative tests ensure software systems' stability and reliability, resulting in higher quality and more robust software applications.