Types of Software Testing to Improve Product Quality

Functional Testing

QA engineers verify that each function of software operates according to requirements. This testing doesn’t deal with application source code. Rather, it works with the results of code functioning and renders system usage. QA specialists provide each function with the needed input, verify output, and compare results with the expected requirements. This test can be completed either manually or via automation tools.

QA engineers conduct functional testing due to:

• Functional requirements. Here, the QA team creates test cases for the process that focus on the prior software functions to undergo testing. QA engineers make sure the functions of the developed product work correctly with different types of input data.
• Business processes that the application must provide. In this case, software testers don’t check the performance of individual software functions. They ensure the operations work correctly under system usage scenarios. Thus, testing is based on use cases.

In short, functional testing capitalizes on software’s features and verifies their working procedures. In turn, these features can be directly related to the day-to-day functions of the product, e.g., logging in, filtering and searching, editing personal data, etc. But they can also involve business functions, i.e., how the software performs in comparison to business goals and whether it delivers expected business value.
Under functional tests, there are numerous types of testing for software development that strive to enhance the product in various areas. So, let’s assess them and see how each can improve your project.

Integration Testing

Usually, a software project consists of software modules created by a development team. Often, one developer codes one module with its individual characteristics. The programmer may accidentally swap the parameters of the function. As a result, an error occurs during the call execution, and multiple modules fail to function together. Once the individual elements of the program are ready, QA specialists start testing their joint performance.

Integration testing verifies the unified functioning of the modules and ensures their smooth operations. During the test, QA engineers first pair the modules, then combine them into large blocks. Finally, the elements must be united into a single system.

QA team conducts the integration testing when:

• Modules interact with APIs and other third-party tools. QA specialists make sure that the API accepts module data correctly.
• Requirements are changed. Sometimes developers deploy new changes that don’t undergo unit testing. Integration becomes a necessity in such cases.

System Testing

Unlike the above, system testing evaluates the entire system or software application as a whole rather than individual components or modules. A fully integrated product may operate in unison with other software or hardware. Thus, the main objective of system testing is to verify that the software system meets the specified requirements and works as expected in a real-world environment.

For instance, an app can request information from external databases. Say, within e-commerce, it can access the list of items available on the vendor’s page or synchronize the delivery time to display this info to a customer. System testing secures this functional junction and ensures that no issues occur during data exchange.

In practice, system testing is usually a combination of both functional and non-functional testing (you’ll learn about the latter further in the text). Omitting system testing can lead to a suboptimal user experience, decreased system reliability, and higher costs due to the need for later bug fixing and maintenance.

GUI Testing

GUI, which stands for “graphical user interface,” is where you interact with the program via images, icons, and any visual elements that help to navigate the system. GUI testing checks if the product user interface system works correctly.

Also, QA experts ensure that the app/software is easy to navigate from the users’ perspective. Since if the visitors aren’t comfortable with the interface or an application is too complex to understand, they will simply leave. The success of software depends on the way users interact with GUI. That is why it is so important to make the GUI bug-free.

Here are a few examples of what QA engineers evaluate during GUI testing:

• Proper size, width, length, position, and clarity of controls of icons, menus, images, buttons, etc.
• Visibility and easy identification of all types of bars (windows, dialog boxes, toolbar).
• Viability and readability of fonts used in a software/app.
• Optimal positioning of GUI elements for different screen resolutions.

Smoke Testing

It detects the most obvious bugs that may occur during the very first stages of software execution. Smoke testing deals with the software build. A build is a “container” of reusable modules, libraries, and data files that implement software functions.

QA experts perform smoke testing when developers code new software functionalities and integrate them with builds. In the process, developers deploy software builds to the QA environment. The task of a QA professional is to ensure the build’s stability, correct functioning of verified features, and faultless running of critical functionalities. If smoke testing is successful, the QA team can start conducting further tests.

Regression Testing

Once the developers receive ready-tested software pieces, they fix the bugs and introduce the needed code changes. Often, these adjustments are the sources for new defects to occur. And regression testing helps to detect them. The purpose of this testing is to make sure that the software changes have no negative impact on the existing functions.

Regression testing is required when:

• Performance issues were fixed.
• The software contains new features.
• Defects were eliminated.
• Requirements were modified.

QA engineers usually conduct a series of 3-5 testing sessions. Although types of manual testing can be applied, it might be expensive and time-consuming. That is why automation is often the go-to for regressions. It saves nearly 60% time for bug detection and 40% in costs.

API Testing

A recent shift to API-based architectures is a powerful innovation driver in the software industry. Web and UI don`t impose critical business risks anymore. Instead, the non-human application programming interface has become far more vulnerable. For that reason, API testing is turning into a crucial part of product quality strategy.

An API is a critical part of any app. APIs contain the functions performed by another system. In such a way, API is a background for data exchange between different software parts. And the task of API quality assurance is to check if software systems co-function correctly. QA engineers determine if APIs work as per requirements regarding security, functionality, performance, and reliability.

API tests focus on software core functionality. API testing accesses an app without a user interface. In such a way, it allows the detection of small bugs that may cause serious problems during the GUI testing stage. QA specialists check if APIs work at all if they easily integrate with other systems and their performance under stressful conditions.

Unlike GUI testing, API quality assurance takes less time to conduct. Nearly 3,000 API tests take 50 minutes, and the same amount of GUI tests require 30 hours. Automation tools for API testing need less code and, therefore, accelerate the QA process.

End-to-End Testing

E2E testing evaluates software’s workflow by simulating real-life scenarios. For an e-commerce website, end-to-end testing might involve simulating a real user scenario where they search for a product, add it to their cart, and complete the purchase. This would involve testing different components of the software system, such as the search function, product catalog, shopping cart, payment processing, and order fulfillment.

To put it simply, E2E testing relies on actual user scenarios to review the outcomes of customer actions from start to finish. From the moment they log in to completing the payment and receiving the order. This testing also allows the detection of any issues with external systems’ integrations and across various software layers, including UI and API.

So if you are yet to conduct E2E testing for your project, consider some of the benefits it presents:

• User-centricity. The most powerful aspect of end-to-end testing is its use of genuine user scenarios to check the functions within. Adopting customer perspective lets QA experts focus on user behavior, and the dev team can adapt the app to be more user-friendly.
• Full coverage. End-to-end testing evaluates all components of the software system, including the user interface, application logic, database, and integration with external systems. This leads to a healthy product that acts as intended and has no major defect that could discourage further use.
• Efficient automation. E2E testing helps identify issues earlier in the development cycle. But it can also be automated, which further reduces STLC, testing expenses, and fixing costs. QA professionals can code multiple tests and run them simultaneously, advancing team productivity and testing efficiency.

Acceptance Testing

This is the final phase of the software testing process. The test evaluates whether the system corresponds to business requirements and is ready for release. The QA team also conducts it considering user needs. Acceptance testing determines if the target audience is satisfied with the software’s use. However, several parties might perform different types of acceptance testing.

Members of the organization that created the software can participate in testing. Usually, the people who didn’t work on the project directly (sales team, product management) conduct Internal Acceptance testing to check if the system is available to use.

Outsourced companies or independent teams provide External Acceptance testing, which can includes:

• User acceptance testing via a simulated target audience of the software who check if they are comfortable with the system use.
• User acceptance testing via end users, i.e., a sample of actual consumers who use the software and offer their direct feedback.

Thanks to this testing stage, clients always have a clear understanding of software specifics. Besides, product owners have a chance to make the project fully compliant with customers` needs.

Non-Functional Testing

This type of software testing evaluates the non-functional aspects of a software system, such as performance, reliability, usability, security, etc. Unlike functional testing, which focuses on the system’s behavior and functionality, non-functional testing is concerned with how well the system performs its tasks and how well it meets the non-functional requirements.

So, functional tests focus on what the software should do, and non-functional tests capitalize on how the software does what it should do. Such testing is not crucial to functionality but significantly impacts user experience.

For instance, consider your app’s loading speed. A customer is able to find what they need – this is a crucial function. How fast the app loads what the client needs does not define whether this function actually works. Instead, it determines how well the software performs. And it is no news that a long waiting time may deter proceeding with the program.

Now, let’s take a closer look at tests that fall under non-functional testing.

Compatibility Testing

Modern apps and websites should run perfectly on different web browsers, hardware, mobile devices, and operating systems. The task of compatibility testing is to analyze system behavior in various environments. The test is performed via two methods:

• Forward testing checks the application’s compatibility with the newest mobile operating systems.
• Backward testing ensures a software created for the latest environment versions also works with older ones. In other words, the behavior of a system should be fully compliant with any hardware/software version.

Here are some of the most common bugs compatibility tests allow to detect:

• Issues with text alignment and font size.
• Broken UI, scroll bar, tables, frames.
• Changes in CSS, color, and style.

The testing prevents financial risks and reputation damage due to poor system compatibility and negative clients’ experience.

Performance Testing

Software functionality is not the only concern for QA engineers. Response time, scalability, and reliability also play a crucial role. The purpose of performance testing is to measure software response time under the expected workload. It prevents software from slow loading when multiple visitors enter simultaneously, inconsistent functioning across various operating systems, and poor usability.

As an illustration, take a look at the performance testing checklist:

• Stability: to ensure that software remains stable under changing load conditions.
• Scalability: to determine the highest user load the software can handle.
• Speed: to check if the system response is quick.

There are several types of performance testing, each focusing on a different aspect of the system’s performance.

Load Testing

Load testing investigates a system’s performance under normal and anticipated peak load conditions. It helps ensure that software keeps running as supposed when many users exploit it concurrently or when processing large amounts of data. Load testing tools create requests for various functions of the system and record the response time, throughput, and error rates.

Say an app is expected to host 10 000 users at once. Load testing would simulate virtual users or generate transactions to mimic the behavior of real users. The normal load could include 5,000-8,000 customers, and the peak load – 9,000-10,000. The latter is extremely important as it allows us to analyze how the app works during peak traffic and prevent downtime.

Briefly, this testing permits:

• Identifying performance issues and bottlenecks.
• Optimizing system performance.
• Ensuring positive user experience.

Stress Testing

This test analyzes system behavior under the conditions of high traffic and data processing for a long time period. It can include many aspects, from appropriate displays of error messages under prolonged, constant, and extreme load conditions to recovery after failure and continued functioning.

QA specialists perform stress testing parallel with load testing, gradually increasing server workload. Once the load is reached, the QA team analyzes and measures response time during the selected timeframe.

Stress testing is helpful under the following scenarios:

• Sudden surge when advertising in leading media.
• Traffic spikes during festive seasons and discount periods.

The test prevents high revenue loss due to possible system failure. Thus, your project is better prepared for abnormal conditions and can provide a positive customer experience.

Spike Testing

This testing type helps your software survive traffic spikes. Often, websites face sudden surges after launching advertising or marketing campaigns to attract consumers. Shopify data demonstrates that Black Friday Cyber Monday shopping weekend riched nearly $1.5 billion in sales during 2018. They predict the tendency to grow even further. It means that modern software must handle traffic surges. Thus, spike testing determines if software can appropriately handle spikes of traffic on a server.

QA engineers focus on:

• Software operating capacity.
• Website sustainability with peak traffic load.
• The maximum number of users to enter the site.
• The ways to make the software scalable for more users to visit.

Spike testing prevents your product from poor performance and detects weak points in the system under tough traffic before the release.

Scalability Testing

Essentially, this testing focuses on the software’s ability to adapt to traffic alterations, be it a spike or fall in user requests. The purpose of scalability testing is to ensure that the system can accommodate future growth and usage without any negative impact on performance.

Scalability testing is typically performed by simulating different load levels and observing the system’s behavior. The testing team monitors various performance metrics, such as response time, throughput, and resource utilization, to determine how the system functions under varying traffic.

This testing is important for every project, but it is particularly crucial for evolving software.

• In 2008, Twitter experienced significant scalability issues due to the sudden growth in its user base. The site was frequently unavailable, and users experienced slow response times.
• The launch of the Healthcare.gov website in 2013 was plagued with scalability issues that prevented many users from enrolling in health insurance plans.
• In 2017, Amazon Web Services (AWS) experienced a major outage due to a scalability issue in its S3 storage service. The outage affected thousands of websites and apps that relied on AWS, leading to significant financial losses for companies that were unable to serve their customers.

Such instances can lead to harmed consumer trust, reputation damage, and financial losses. So it is critical to cooperate with QA professionals who know when is the right time to test for scalability.

Security Testing

Security testing is an essential aspect of software development that aims to identify and mitigate potential vulnerabilities and threats that may compromise the security of a system. Because cybersecurity is often the number one priority for software, security testing includes a range of techniques and methodologies that simulate attacks, vulnerabilities, and other security risks to evaluate the system’s robustness and resilience.

• Penetration testing involves simulating attacks on the system to identify vulnerabilities that could be exploited by an attacker, e.g., weak passwords, unsecured network configurations, etc.
• Vulnerability scanning capitalizes on automated scans of the system to quickly identify common vulnerabilities, such as missing security patches or misconfigured servers.
• Code review relies on manual testing to examine the system’s source code and locate security issues. It focuses on identifying coding errors and security flaws that could be exploited by hackers.
• Threat modeling analyzes the system’s design and architecture to find potential security risks. This testing allows for early security risk identification and system design with security at its core.

Nowadays, businesses should never compromise on security testing, as they might have to deal with grave consequences. For instance, in 2020, an online fashion retailer Shein experienced a data breach that compromised names, email addresses, order details, billing and shipping addresses, and partial payment card information of millions of customers.

As a result of poor security testing, the company had not implemented proper encryption measures and stored user data in an unsecured database that was easily accessible to anyone with basic hacking skills. Hence, the company’s reputation was negatively affected, and it was forced to issue a public apology and offer free credit monitoring services to affected customers.

So, it is always better to invest in proper cybersecurity to protect your client’s information and business assets.

Accessibility Testing

Accessibility testing is a crucial process that ensures that the software is accessible to anyone, regardless of their physical or cognitive abilities. It stands out from other types of testing in software development as it is essential for creating a more inclusive and accessible digital environment.

Accessibility testing involves assessing the software’s design and functionality to ensure that it meets the requirements of various accessibility standards, such as the Web Content Accessibility Guidelines (WCAG). This testing process involves evaluating how the application interacts with assistive technologies, such as screen readers, magnifiers, and keyboard navigation, to ensure that users with disabilities can effectively use the software.

QA professionals who are proficient in accessibility testing can substantially upgrade your software and save the project from legal troubles.

• Accessibility testing promotes equality by providing ample opportunities to any person, which is great for strengthening brand image.
• It is a crucial element for positive CX and is useful even for people with no disabilities as it encourages user-friendliness.
• It can also help organizations avoid legal and financial consequences resulting from non-compliance with accessibility standards, e.g., WCAG 2.0, Rehabilitation Act Section 508, and ADA in the US or WCAG 2.0 and European accessibility standard EN 301 549 in the EU.

Localization Testing

Cultural patterns and language are the areas of interest for localization testing. It customizes the software/app per the targeted country and its linguistic peculiarities. In the process of localization testing, QA engineers must:

• Verify content errors.
• Check the UI compliance with the cultural specifics.
• Test if the default language, date/time format, and currency are designed according to the targeted country.

In such a way, QA specialists ensure your target audience feels comfortable on your website, as it behaves according to the local cultural patterns.

Exploratory Testing

Exploratory testing is a more hands-on, experiential approach to finding and documenting software defects. Unlike scripted testing, exploratory testing does not follow checklists or test cases. Instead, QA specialists are free to explore the application, trying out different scenarios and interactions to find unexpected issues and potential areas of improvement.

This testing centers on reviewing the application to identify defects and enhancement vectors in terms of how the application works. But it can also incorporate non-functional aspects of the application, such as usability, performance, security, and accessibility.

While exploratory testing is not a substitute for more narrow and dedicated tests, when it is combined with other types of testing in SDLC, it can be a great advantage.

• Its integral flexibility and adaptability let QA experts adjust their approach as needed to account for changes in the software or testing environment.
• Because exploratory testing promotes creativity and innovation, it allows for uncovering defects that could be missed with more scripted testing methods.
• It can be done relatively quickly and efficiently, as it does not require a predetermined test plan or set of test cases.

To Conclude

The types of testing in software engineering discussed today are just the tip of the QA iceberg. And to release a bug-free, flawless product, QA specialists must be proficient in each as well as apply effective testing methodologies and viable software tests. That is why it is important for business owners to be familiar with QA processes and practices – it will help you find the right QA partner and be more confident with your choice.