Negative vs Positive Testing? Always Go for Both! Here’s Why

Technological advancements have outpaced any innovation in human history. With 50 million startups emerging each year, the competition to stay on the market is intense. This race of digital projects propelled the significance of software testing services to a new level. But does it mean the approach to testing should change along with the pace of innovation?

Yes and no. More companies have started looking into test automation and reskilling of QA engineers. Yet, quality assurance still has positive and negative testing at its core. And it will remain so no matter what technologies teams apply.

This article will help you understand how positive and negative testing work and why they always do best in tandem.

Positive Software Testing: Definition & Purpose

Positive testing, also called happy path testing, validates a system’s functionality through correct inputs. It ensures the software’s ability to handle typical and ideal user interactions.

Examples & Scenarios

Positive testing shows how a system responds to “appropriate actions.” Here are a few examples to make this more clear.

• User registration. Positive testing verifies that the registration proceeds successfully when a person uses valid information. The software should recognize proper inputs (username, email, and password in a format that matches the requirements) and accept them.
• Valid login. Logging in with the correct credentials should confirm that a system validates them. In other words, the app reads the data, recognizes it, and displays the functionality for registered users.
• Access control. Only authorized users can enter specific parts of the system’s functionality. For example, those with Admin rights can publish information on all website sections, while those with HR rights can only access job postings.

Advantages of Positive Testing

• It validates the functionality. Positive testing serves as a means to confirm the expected. QA engineers prove that the software can perform the tasks it was designed for.
• It verifies compliance with requirements. Positive testing ensures the software aligns with the documented specifications, development efforts, and client or stakeholder demands.
• It ensures correct system behavior. Positive testing confirms that the system responds correctly to user actions or highlights mistakes in system behavior.
• It establishes a baseline for performance. Positive testing sets indicators for evaluating how the system handles varying workloads.
• It confirms user acceptance criteria. When positive test cases pass, it means that the system meets the requirements for acceptance, paving the way for further enhancement.

Negative Software Testing: Definition & Purpose

Negative or error path testing evaluates how a system responds to unexpected conditions and unusual scenarios. It seeks to detect and prevent deviant software behavior and ensure it doesn’t do what it’s not supposed to. It answers questions such as:

• Can a user complete an action if they submit incorrect data?
• How does the system respond to data that exceeds predefined limits?
• How robust is the system’s error-handling mechanism?

By addressing these, negative testing becomes a proactive measure to enhance software resilience, security, and reliability.

Examples & Scenarios

Negative testing isn’t about reversing a positive test case (even though it works like that sometimes). Below are several examples of how it works in practice.

• Empty fields. Consider a user trying to register on a website. If they leave a required field blank, the system should display an error message, guiding the user to fill in the necessary information.
• Incorrect username or password. When a user enters incorrect login details, the system should respond appropriately – deny access and show a corresponding error message.
• Access control. Here, a person can try to use some part of the system that is beyond their access level via a direct link. It can be a premium feature on a free membership plan or a link for editing a service landing page for an HR manager who is only allowed to work with “Careers.”

Other common negative testing scenarios include:

• Using invalid data: testing the system’s response using data that does not meet validation criteria (e.g., typing or pasting text instead of numbers, putting a home address in the phone number field).
• Exceeding the character limit: evaluating how the system manages input that surpasses specified character restrictions.
• Allowed data limits and bounds: ensuring the system behaves correctly within defined data limits and boundaries (e.g., creating a password with five symbols when the minimum length is eight).
• Reasonable data inputs: testing with data that falls within expected, realistic ranges (e.g., a user tries to purchase 1000 identical items of a single product).
• Web session testing (access): verifying user access control to assess how well the system safeguards restricted areas.

Advantages of Negative Testing

• It identifies vulnerabilities & weaknesses. Subjecting a system to atypical scenarios is a way to reveal flaws one can miss when working with correct inputs only.
• It enhances system security. Negative testing focuses on deviant user behavior, ensuring the system can prevent unauthorized access and maintain data privacy.
• It validates error-handling mechanisms. Initiating failures is the best way to see whether a system provides correct and clear error messages.
• It tests boundary & edge cases. These are the areas most prone to bugs, and increased attention to boundary and edge cases ensures the software can work with all values within the set ranges without breaking or degrading.
• It explores non-standard user interactions. Clicking buttons rapidly, navigating away from pages during critical processes, or attempting unconventional workflows uncover more bugs and improve a product’s overall stability.

Positive vs Negative Testing: Key Differences

It seems that positive and negative testing should only come with “vs.” in between, as the naming suggests opposing one another. However, positive and negative testing should always come together. It is never “either… or…” but a combination of both to ensure sufficient test coverage. The reason lies in the particularities of positive and negative testing.

Goals and Objectives

• Positive testing focuses on verifying expected outcomes, i.e., predicted actions that lead to successful completion of an action. It focuses on typical, expected user behavior and follows “correct” paths to confirm the correct results.
• Negative testing centers on contradicting user behavior where system logic is disrupted. It’s about using software in real-life conditions, not how developers and stakeholders expect one to use it. With negative testing, QA engineers examine how a system handles unintended behaviors.

Designing Positive & Negative Test Cases

Both positive and negative testing involve boundary value analysis and equivalence partitioning. Yet positive uses the valid data pool, while negative ventures outside the accepted limits.

• Positive test cases are designed to verify the software’s functional correctness per the requirements and use cases. They are easier to create compared to negative tests. The reason is simple: they tackle likely, typical user actions, following the requirements.
• Negative test cases are designed to trigger errors. They can be more challenging to create, as requirements typically don’t cover unintended behavior. Positive tests can be a reference for negative ones, but experience and creativity help extend the pool of unintended.

Positive and Negative Testing in Practice

In a perfect world, there is enough time and resources to ensure close to a hundred percent test coverage. In reality, however, companies often have to compromise. By now, you must know that skipping the QA part isn’t a good idea, and neither is omitting negative testing. The following tips help to strike the right balance.

Combining Positive & Negative Testing

The most effective quality assurance strategy involves combining positive and negative testing. It is how QA engineers can ensure that software meets functional requirements and withstands unexpected scenarios and security threats. If a deadline or budget is tight, it is okay to cover only business-critical functionality with negative tests.

Situational Context and Project Requirements

As often happens in quality assurance, the answer to “How much negative testing is enough?” is, “It depends.” It is always determined by situational context and project requirements.

• Positive testing is ideal for validating expected functionality and correctness when developing standard applications with known user behaviors.
• Negative testing comes into play when there’s a need to uncover vulnerabilities, enhance security, and address potential failure points.

Here are some situations when negative testing can be minimized:

• When the application or system has a very limited scope and functionality, e.g., a simple calculator app that performs basic arithmetic operations.
• When the app is designed for a user group with a high level of technical expertise who are extremely unlikely to deviate from standard behavior.
• When a system is not expected to handle complex or critical data, e.g., a note-taking app that doesn’t store sensitive information.
• When a system is built using robust and well-tested frameworks or libraries. They often have built-in error handling and security features that can help mitigate potential issues.

When negative tests are not extensive, they must be supported by more comprehensive positive tests to balance the gap.

Common Misconceptions About Positive & Negative Testing

Misconceptions about testing methodologies leave a footprint on a QA strategy and affect the quality of the final product. So, let’s do some myth-busting before moving to the best practices.

Myths About Positive Testing

#1. Positive testing is sufficient for quality assurance.

Positive tests cover a defined scope of scenarios. They are limited in what they can do for a project. Relying solely on positive testing can leave a system unprepared for real-world usage conditions.

#2. Positive testing is faster and, thus, more efficient.

It is indeed more straightforward. Back to the registration flow, there is only one way to pass it correctly: by entering valid data. Meanwhile, negative testing entails registration with one or many empty fields, as well as different combinations of incorrect inputs.

So it is faster but at the expense of the efficiency. It is not enough to uncover critical vulnerabilities and weaknesses.

#3. Positive testing is less important for complex systems.

Positive testing remains central for confirming expected functionality. Negative testing becomes even more crucial for addressing the increased risk of vulnerabilities within intricate systems.

Myths About Negative Testing

#1. Negative testing only identifies edge cases.

Negative testing does examine how the system responds to edge inputs beyond the set ranges. However, edge cases are only one of many unexpected conditions negative testing works with. They are only one of many ways to “disobey” the rules of a product.

#2. Negative testing is about breaking the system.

Some attempts to break the system may be included, but the main goal is different. It is not to break something but rather to uncover vulnerabilities. The system doesn’t necessarily break when a QA engineer feeds incorrect inputs or alters a usual flow. The goal is to detect the areas where software doesn’t know how to respond to non-standard interactions.

#3. Negative testing slows down the testing process.

Negative testing may require more effort, as a team needs to work with more items on a checklist or design more test cases. Yet, uncovering vulnerabilities and weaknesses early in the development cycle is always best for the project.

Best Practices for Positive & Negative Testing

Last but not least, a few words on how-tos. Much still depends on the context, software features, and tech stack. So, let’s focus on a few general rules that would be useful to understand.

Best Practices for Positive Testing

• Thorough coverage of positive scenarios helps validate software functionality for standard user behavior. Broad coverage also aids in uncovering possibilities for negative testing. The former will offer more ideas on what could go wrong, thus advancing negative tests and product quality.
• Formulating clear expected outcomes is fundamental for testing objectivity and precision. It is what allows one to distinguish a bug from a feature. Without this, all that’s left is assumptions.
• Know the customer audience to test software from an end-user perspective. Pay attention to how easy it is to take the “happy path” and don’t fall under the curse of knowledge. A goal of QA is to ensure that a) the software works and b) it doesn’t confuse users.

Best Practices for Negative Testing

• Cover a wide range of negative scenarios to locate more vulnerabilities and weaknesses. It seems obvious, but the obvious things are often the first to forget about.
• Pay close attention to boundary values of acceptable inputs and conditions where errors tend to pile up. Testing near these boundaries helps detect issues related to buffer overflows, data truncation, and unexpected behavior at the extremes.
• Examine the system’s error-handling mechanisms by triggering errors and exceptions intentionally. Call this caution or the art of anticipation in action, but it’s always better to be a step ahead of a user, especially a tricky user.

To Sum Up

“Positive and negative testing” sounds like the yin and yang of quality assurance. We usually leave out the “positive” when using the term (which makes sense). Some decide to leave out negative testing from testing plans (which doesn’t).

In practice, together, they enable broader and more accurate test coverage. Verifying software’s behavior against the requirements is fundamental. Checking whether it doesn’t do what it isn’t supposed to do may seem secondary, but this is equally important.