Testing is one of the most important processes in software development. It is what makes your software robust and error-free. In today’s competitive scenario, it is crucial for companies to deliver software of high quality. To do so, they acquire a balanced approach towards all the phases in the software development methodology – from design to development to test to release. Most of the time it already becomes clear during the design phase what all scenarios need to be covered during the testing process. But as the product development proceeds, the developers encounter more complex logic and scenarios that they incorporate while programming. Hence, by the time the project reaches the testing stage, the team has already known all the areas of the software that must be tested thoroughly. Now, testing is basically of two types – Positive and Negative testing. Positive testing is done to validate the software’s behaviour against expected behaviour whereas negative testing is done to check how software responds against unexpected input. Both kinds of testing are necessary to ensure your software doesn’t break in any case.
In this article, we will explore positive and negative testing in detail and provide tips and suggestions to master this practice.
What is Positive Testing?
Positive testing is the first form of testing where the functionality of the software is checked against the basic requirements. While performing this, a tester inputs valid values to the software and checks if the software produces required results or not. For any software to be useful, it should first pass the basic test of executing the requirements correctly. Only after the basic functionality is tested and found out to be working correctly, must the tester proceed to test the software for other scenarios too.
Examples of Positive Testing
- Entering the correct login details while signing in.
- Entering all the details correctly while submitting a form.
- Performing an online bank transaction by providing valid account details and sufficient bank balance.
- Entering a valid pin code in the address field.
Once such inputs are provided and the software is made to run, a positive test ensures that the software produces results as per the requirements.
Key Benefits of Positive Testing
- Ensures requirements are implemented correctly.
- Builds user confidence for the usage of product.
- Creates a baseline assurance of the software to be validated later against unexpected scenarios.
What is Negative Testing?
When you want to turn your software into a robust and unbreakable system, negative testing is the way to go. It tests the behaviour of your software during unexpected conditions and input scenarios. The requirements always specify certain rules for the software to produce results. And when those rules are not met, how software should behave must also be pre-designed. Negative testing looks into the latter part and makes sure that the software behaves as expected under negative conditions.
Examples of Negative Testing
- Invalid login details during signup.
- Invalid email-id entered into the field.
- The mandatory input field in the form is left blank.
- Conducting a bank transaction for an amount bigger than the account balance.
Key Benefits of Negative Testing
- Ensures if the error messages are being displayed correctly.
- Makes the system more robust and resilient to run successfully even in the adverse scenarios.
- Eliminates the risk of security loopholes.
- Eliminates the chances of system breakages.
When to use Positive and Negative Testing?
So far, it has become clear the role of both kinds of testing. Now, let’s discuss what are the specific stages when these tests should be used. To start with, positive testing should be used in unit testing, system testing and integration testing while negative testing should be used in security testing and user acceptance testing (UAT). Let’s elaborate on this.
Positive testing is especially important in the initial stages of the development when a developer themself can test the system by providing a valid input. The software is always designed initially to work on fulfilling the requirements first. Hence, the testing should also be done initially for those requirements by providing the ideal inputs and conditions for it to work properly. During unit and system testing, an AI testing tool can check by providing the right input if each module is working as per the expectations or not. In integration testing, the calls between different applications are tested by giving the correct parameters. If it all works properly, the first phase of testing is considered as completed.
Negative testing comes after all the expected requirements have been met by the software under ideal conditions. Now the software must be tested not just for producing required results but for how it handles the unexpected inputs. This ensures how resilient your software is. Negative testing is often performed thoroughly on applications dealing with sensitive data like in financial transactions or while maintaining user data privacy. E.g. when wrong credit card details are entered or when a mandatory field is left blank, your software must handle it gracefully with appropriate error messages. A negative test case ensures that the application doesn’t become unresponsive during unexpected situations but guides the user to the right action through an informative error message.
Metrics to Measure Test Efficacy
Metrics are useful to measure how effective your testing process is. Without metrics you would not be able to know what all areas you have covered, how many defects you found, and the efficiency of your testing strategy. Only by measuring them all can you work towards improving your testing process. Few metrics worth measuring are:
- Test Coverage: Test coverage measures the percentage of features, functionalities, requirements and program logics that have been covered by the test cases. It allows you to check the balance between positive and negative test coverage and thereby judge how much weightage is given to checking the expected behavior vs error handling capabilities.
- Defect Detection Rate: Even after a thorough testing and software release, few defects are still found in production. A defect detection rate (DDR) measures the proportion of defects found during testing versus errors found in production. A DDR entails lesser chances of your system to break in production.
- Defect Leakage: Defect leakage indicates defects that were missed in one testing phase and discovered in the next phase. The most common cause of defect leakage is poor negative testing. Edge-cases were not tested in the initial testing but done in the later stages to discover bugs in error handling.
- Automation Coverage: This shows how many test cases have been automated in your test suit. Most of the test cases that are repetitive during positive and negative testing must be automated. The automation coverage decides your test efficiency and the overall time to release your product after a thorough testing. The more automation, the faster release.
Bottom Line
Positive and negative testing are the two sides of the same coin. One ensures usability while another ensures reliability and security. It is crucial to ensure that your software doesn’t just fulfill the requirements successfully but also behaves intelligently for any discrepancy in the input. This shows that the software was designed while keeping all the possible scenarios in mind. There’s nothing worse than finding a software unresponsive when a user unintentionally enters wrong data. Hence, to enhance the quality of your software, it must be tested against all the possible scenarios a tester can think of.
