Techniques to Perform Negative Testing

Introduction

Software testing is pretty vital when conducting software development projects. There was a time when this was considered as an afterthought however, in the present scenario this is not the case, today the relevance of software testing shouldn’t be neglected at any rate. Now software testing is a pretty wide concept, so we won’t be able to discuss every topic under this hood. As the title suggests, the following post focuses on negative testing, what it is all about, how it is beneficial, and what are the best techniques to consider when performing negative testing.

What is Negative Testing?

Now what is software testing all about? It is a very important process for checking if all the features and functionality of the app work in the right manner as pre-determined. Also, here you will be able to find out whether the app is capable enough to handle all the challenging situations and inputs or not.

Negative testing often known as failure testing or error-based testing is conducted to spot negative characteristics of the app. This is supposed to be done by designing a wide range of test cases, and above all what would be the output against incorrect input.

In other words, this is a process of offering unexpected and invalid inputs into a system. No wonder this type of testing is also known as fault injection, a technique mainly used to introduce errors and faults within a system just to test how things respond. Negative testing ensures locating bugs and fixing them right before the launch.

Now here the method is a bit different, you are purposely introducing errors into the system just to find out how it responds. This is a bit counterintuitive, yet necessary to uncover potential vulnerabilities and bugs. Also, costly late-stage fixes and potential customer dissatisfaction can be well taken care of.

• The system is well-authorized to offer invalid data as input

• No matter what, the product won’t fail especially in case of an unpredicted input

• Failure testing or error path testing

• Quick spotting of negative characteristics

Before we put our hands on the purpose of negative testing, it’s time to unveil the characteristics of negative testing.

1. Evaluating security breaks - Finding potential security breaks is possible, especially during handling procedures.

2. Display data corruption - Absolute showcase of security violations and data corruption.

3. Identify defects - Mainly performed to identify defects and if not caught in time, it can lead to essential breakdowns.

4. Uncovering software vulnerability - Uncovering potential software vulnerabilities and scope for exploitation.

5. Stabilize applications - The overall stability is guaranteed of the developed app

6. Finding loopholes - Lastly, negative testing assists in finding critical loopholes and weak areas which at some point result in failures.

Purpose of Negative Testing

The ultimate objective behind negative testing is to uncover potential errors and security vulnerabilities which might not be found due to positive testing especially when the tester uses valid inputs.

This is mainly done to evaluate a software system’s behaviour, especially in regard to invalid and unexpected inputs.

• Functions as a critical component of software quality assurance mainly considered to validate if the system behaves as expected and meets proper customer requirements

• If the system behaves gracefully especially when facing invalid inputs ensuring a better user experience and reduces the risk of user frustration.

• Probably assists in identifying and fixing stability issues which might not be discovered through positive testing.

Types of Negative Testing

1. Boundary value testing - Here testing the system is possible using different inputs which are at minimum and maximum limits of the input range.

2. Input validation testing - It is possible to test the system’s handling of invalid inputs such as invalid data types, out-of-range values, and invalid characters.

3. Exception testing - Here exceptional conditions are tested such as missing data, unexpected shutdowns and other exceptional events.

4. Load testing - The next type of negative testing is load testing. This one includes testing of the system behavior especially during heavy loads and stress, let’s say during high traffic conditions or high-volume data processing.

5. Compatibility testing - Here negative testing is done to check whether the system is highly compatible with different hardware and software and network configurations.

Positive Testing vs Negative Testing - The Difference

As the name itself suggests, positive and negative testing are poles apart but both of them do matter to a great extent. Positive testing is all about verifying that the software present under the test performs as per the given requirements. Here it is ensured that every feature and functionality works right in accordance with the predetermined expectations. Unlike negative testing, valid input is highly given priorities and if everything goes right, there is nothing to worry about. Whereas when it comes to negative testing, invalid input and conditions are given just to see how the developed app reacts in case of any issues or challenges.

Both are a necessity, not every time the situation would be in your favour. And test cases will pass if the actual result matches the expected ones.

When to Consider - Positive and Negative Testing

Positive and negative testing must begin pretty much early in the software development process to catch defects or else the repercussions can be pretty disappointing. Testing teams should consider both positive and negative tests from design control to spotting all kinds of functional risks.

Try including as much positive and negative testing throughout the development process as possible especially during smoke testing and sanity testing.

Being one of the most high-level tests, smoke tests ensure quality gate and in-depth test runs whereas sanity tests are pretty different from these. They are informal and unscripted tests just to make sure everything is verified at a high-level.

Now negative tests on the contradictory can be pretty destructive. This is the reason why these tests aren’t recommendable in post-production deployment checkouts or in production environments. Also, in other words, negative testing shouldn’t be used in smoke and sanity testing. No wonder this type plays an important role in non-functional testing and user experience.

How is Negative Testing beneficial in the software development process?

• Identify how the system behaves, is it as per pre-determined expectations or not. This needs to be when an invalid or unexpected input is incorporated.

• After identifying the root cause, negative testing can assist in improving the overall quality of the software and making it more flexible, scalable and robust.

• Seamlessly taking care of all the security vulnerabilities, especially in case of invalid inputs

• Testing under some adverse conditions, negative testing can ensure functions are correctly used in real-world scenarios.

Top Negative Testing Strategies

1. Boundary value analysis

The first and foremost method of negative testing includes writing test cases for values outside the boundary limits. Let's say for example, if the

Boundary limits are 1 to 100 then it means you are testing a text field where it accepts data within the 1 to 100 character range.

Some of the popular examples of BVA include:

• Accepts ages from 1 to 100, test cases need to include values such as 0, 1, 100 and 101.

• If the system accepts dates from January 1, 2000, to December 31, 2099, then test cases must be on dates such as December 31, 1999, January 1, 2000, December 31, 2099, and January 1, 2100.

• In the case of a user name field which accepts 5 to 15 characters, test cases must include strings of lengths 4,5, 15 and 16.

• Error Guessing

The next amazing strategy for conducting proper negative testing is error guessing. This process pinpoints specific conditions that trigger failure or error messages. It is always relevant to look for correct issues without a system crash. An incorrect result might lead to extreme downstream failure, especially if things go out of proportion.

3. Input validation Testing

The next amazing strategy is input validation testing. Now this one is very important to verify how the software handles invalid data types, missing fields and unexpected characters. Here it is possible to test apps pretty gracefully by managing erroneous inputs without crashing or any unexpected outcomes.

• Testing invalid types

• Checking for missing fields

• Exploring characters, especially the unexpected one

Conclusion

Of course, this is certainly not it. There are several other strategies, such as checklists, anti-patterns, exploratory testing, and small-scale automation, each one of a kind. In addition to that, these procedures can be time-consuming but worth the risk. If you aren’t sure about the strategy to pick, feel free to reach us out, we will be happy to help

I hope you did find the post worth considering, especially when it comes to negative testing. Good luck!