What is application testing?
Best practices Management
24 mins read
October 12, 2023

What is application testing? complete guide

There is a lot of sweat behind making apps perfectly react to your every touch and swipe, and the unsung hero is application testing. In today's ever-growing tech landscape, app testing has emerged as a non-negotiable step in delivering robust, reliable, and user-friendly software. So, whether you're a curious tech enthusiast or a seasoned QA specialist, sit close: we dive into the world of application testing.

Sylwia Mazepa
Nurlan Suleymanov

What is app testing?

App testing, or application testing, is the process of identifying and assessing software applications’ functionality and performance against product requirements and user experience standards. 

App testing is like quality control for software applications. Testers simulate real-world usage scenarios, interact with different elements, and evaluate the app’s behaviour to uncover bugs, glitches, or usability issues. In app testing, you analyse the performance under various conditions like varying network speeds or many concurrent users. App responsiveness, load times, and resource usage are assessed to ensure stable performance. By thoroughly testing the application, you can identify and fix issues before you deliver the app to users’ hands, improving user experience, customer satisfaction, and reputation.

Categories of application testing

Several criteria can categorise application testing, one being the platform you use. This way, we can talk about three main types of application testing.

1. Web application testing

Web application testing is the process of ensuring reliable performance, seamless user experience, functionality, compatibility, and security of web applications, regardless of browsers, operating systems (OS), and devices. 

Various aspects are examined during this testing to identify potential issues: 

  • Compatibility testing monitors the application’s performance across various browsers (Chrome, Firefox, Safari) and OS. 
  • Responsive design testing evaluates an application’s ability to adapt and display flawlessly across various screen sizes, including desktops and mobile devices. 
  • Adaptive design testing goes beyond responsive design by tailoring the application’s layout, content, and functionality to suit different devices and resolutions explicitly.
  • Performance testing focuses on the application’s responsiveness and stability under different network conditions, measured by page load times, data processing speed, and resource usage.
  • Security testing detects and addresses vulnerabilities, like cross-site scripting (XSS) or SQL injection, which could compromise the application’s data integrity or expose it to malicious attacks.

2. Desktop application testing

Desktop application testing is the evaluation and validation of software applications that are designed for desktop or laptop computers. This testing aims to ensure these applications’ functionality, usability, compatibility, and performance on different OS, hardware configurations, and user interfaces. 

Different tests are conducted on various aspects of desktop applications, including the following: 

  1. Functional testing to verify all features and functionalities of the application 
  2. Usability testing to evaluate the user-friendliness of the application through interface design, ease of navigation, and overall user experience
  3. Compatibility testing to ensure the application’s functionality across different OS (Windows, macOS, or Linux) and hardware configurations 
  4. Performance testing to assess the application performance through responsiveness, resource utilisation, and stability under varying workloads 

Desktop application testing also includes installation and uninstallation testing to ensure you can install the app smoothly and error-free. Additionally, depending on the application’s specific requirements, you might consider compatibility with peripheral devices and network connectivity.

3. Mobile application testing

Mobile application testing evaluates and validates software applications specifically designed for smartphones and tablets. It focuses on ensuring these applications’ functionality, usability, compatibility, performance, and security on different mobile platforms, such as iOS and Android. 

The key areas of mobile application testing include:

  • Functionality: Testing the application’s features, interactions, and user flows 
  • Usability: Evaluating the user interface, navigation, and overall user experience 
  • Compatibility: Verifying the application functions correctly across various mobile devices, screen sizes and OS versions
  • Performance: Assessing the application’s responsiveness, speed, and resource utilisation 
  • Security: Testing for vulnerabilities, such as data leaks, unauthorised access, or insecure storage 

You can also test mobile applications for specific features like GPS, camera, accelerometer, and push notifications.

Types of application testing

There are several types of application testing, and we will talk about them one by one.

1. Smoke testing and sanity testing

Smoke and sanity testing are software testing techniques that test an application or system’s basic functionality and stability. Here’s a brief overview of each: 

  • Smoke Testing: Also known as build verification testing (BVT), smoke testing is used to quickly check an application’s critical functionalities or system. It is generally conducted before more extensive testing phases to identify critical issues that could prevent further testing. Smoke testing focuses on major functionalities and core features rather than exhaustive testing. It helps ensure the application is stable enough for further testing. 
  • Sanity Testing: A narrow, focused testing form that aims to verify specific app functionalities or components. Sanity testing checks the impact of recent changes or bug fixes on the app’s functionality. It is typically performed after major modifications or bug fixes and focuses on targeted areas rather than surface-level verification that the app does not break down. Sanity testing saves time and effort by quickly identifying new flaws and regressions in the application. 

Both smoke and sanity testing provide a quick assessment of the application’s basic functionality and stability. They identify critical issues earlier in testing and ensure the application is ready for further, in-depth testing. These techniques are a preliminary check to ensure the application meets the minimum requirements and is stable enough for additional testing activities.

2. Regression testing

Regression testing verifies that recent changes or new features in an application have not reintroduced previously solved defects or caused any existing functionality to break. It ensures that the application’s previously tested and working features continue functioning as expected after updates, bug fixes, or system enhancements. 

Regression testing primarily focuses on identifying and detecting unexpected regression issues that might have occurred after changes in the application. It involves retesting the impacted areas and related functionalities to ensure they work correctly and are not negatively affected. 

Depending on the application size and complexity, regression testing can be conducted manually or automatically. It is mainly performed after every significant change or release to mitigate the risks associated with introducing new changes into the application and ensure high performance. By integrating automated regression tests into the CI/CD pipeline, you can achieve reliable feedback faster on code changes and be able to catch and address potential issues early in development.

3. Acceptance testing

Acceptance testing determines whether an application meets the specified requirements and satisfies the needs of the end users. It focuses on validating the functionality, usability, reliability, and overall suitability of the software from the perspective of the intended users. 

Usually, an acceptance testing tool is used to test the application after functional and system testing, involving real-world scenarios and user-like interactions to simulate the actual usage of the software. Users execute test cases, perform tasks, and provide feedback on the application’s behaviour and performance during this testing.

This testing phase can identify gaps between the system’s functionality and intended usage, allowing for necessary adjustments or refinements before the software’s final release. The more frequent usage, however, invites future end-users to check that QA did not miss any flaws in executing real-world scenarios due to the limited understanding of the domain. At that point,  feature additions are usually out of the scope. 

  • Alpha testing is a type of user acceptance testing conducted in a controlled environment, usually by the software development team. It aims to assess the application’s functionality, performance, and overall usability before it is released to a larger user base. The testers can also closely collaborate with the development team, providing valuable feedback and identifying issues or areas for improvement.
  • Beta testing is the second form of user acceptance testing that involves releasing a pre-release software version to a chosen group of external users. These users evaluate the application in real-world environments and provide feedback, including identifying defects, suggesting improvements, or reporting any issues. Beta testing helps gather valuable insights from a diverse user base and allows the development team to validate the software’s performance, usability, and compatibility across various configurations.

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4. Functional testing

Functional testing is another type of software application testing that focuses on monitoring the functional requirements of an application. During this type of testing, you check the software’s individual features, functions, and interactions to validate the software’s behaviour against the specified functional requirements. 

Test cases are designed and executed during functional testing to evaluate different scenarios involving inputs, expected outputs, and comparisons to check actual outputs against expected results. Functional testing covers user interfaces, data manipulation, system interactions, calculations, and business processes. 

The key elements of functional testing are:

  • Validating input and output, including testing boundary values, invalid inputs, and typical use cases. 
  • Verifying system behaviour through evaluating error handling, notifications, messages, and system responses. 
  • Testing business rules and workflows via different scenarios and evaluating if the software accurately performs calculations, validations, and decision-making.
  • Assessing data integrity and manipulation of the software through its ability to store, retrieve, update, and manipulate data correctly.

5. Non-functional testing

Non-functional testing is a software testing type that focuses on monitoring the application or system beyond its functional aspects. Unlike functional testing, it assesses the software’s quality aspects, and the key elements are as follows:

  • Performance testing evaluates your application’s responsiveness, speed, stability, and resource usage under varying workloads, monitoring performance benchmarks and ensuring a smooth user experience, even during peak usage.
  • Usability testing includes gathering user feedback to analyse the application’s user-friendliness and identifying potential UI issues and overall user experience.
  • Security testing aims to identify code vulnerabilities and weaknesses in the application, guarding it against potential threats and protecting sensitive user data.
  • Compatibility testing monitors whether the application functions as intended across different devices, OS, browsers, and versions, ensuring a consistent user experience.
  • Reliability testing verifies the application’s stability over an extended period, ensuring it can handle long-term usage without unexpected failures.
  • Scalability testing assesses the application’s ability to handle increasing data, traffic, or users, ensuring its growth without compromising performance or user satisfaction.


Performance testing is a type of application testing that evaluates an application’s responsiveness, scalability, stability, and resource utilisation under different workloads and conditions. The primary goal of performance testing is to identify any performance-related issues or bottlenecks via a thorough evaluation. It measures various aspects of the application, including:

  • Response time reflects the application’s time to respond to user actions or requests and the speed of individual transactions or operations. 
  • Throughput checks the system processing rate and a specific number of transactions or requests per unit of time, indicating the system’s capacity to handle a given workload. 
  • Scalability assesses how well the application handles increased workloads, determining whether the system can scale up or down efficiently without compromising performance. 
  • Application load testing tests the application’s performance under expected user loads to identify performance issues related to response times, throughput, and resource usage. 
  • Stress testing evaluates the application’s performance under extreme workloads to determine its breaking point. This helps to identify performance bottlenecks, stability issues, or system limitations.
  • Endurance testing determines the application’s performance over an extended period by subjecting it to a sustained workload, identifying performance degradation, memory leaks, or resource exhaustion.

"Only conducting performance testing at the conclusion of system or functional testing is like conducting a diagnostic blood test on a patient who is already dead."

Scott Barber, Performance testing expert

7. A/B testing

A/B testing, also known as split testing, is the comparison of two or more app interfaces to determine the better version. It is a powerful technique used in data-driven decision-making to optimise user experience. 

Here’s how A/B testing works: 

  1. The hypothesis is formulated regarding a specific element or variation that could potentially improve the desired metric or objective. 
  2. Variations (A and B) of the element are created; version A usually represents the existing design or content, and version B introduces the proposed change. 
  3. Test execution includes users divided into groups, each exposed to one of the versions. User interactions and responses to these variations are tracked and measured. 
  4. Data analysis measures key metrics and compares the different variations via statistical methods employed to determine the significance of the results. 
  5. A conclusion is drawn based on the data analysis, deciding which variation performed better in achieving the desired goal. If Version B outperforms Version A significantly, it may be implemented as the new default. 

It is worth noting that A/B testing requires careful planning, sufficient sample sizes, and accurate data analysis. It is an iterative process, with multiple rounds of testing and refinements, aiming to improve and optimise the tested elements continuously.

Testing techniques

Application testing also has various methodologies, including the following three:

1. Black box testing

Black box testing is a testing technique where the application testers do not consider the internal structure, design, or code of the application that will be tested. The focus is solely on inputs and expected outputs. The application is indeed treated as a “black box”: the testers examine its functionality and behaviour without knowing its internal workings. 

QA specialists interact with the application using different inputs and evaluate its outputs during this testing. The goal is to identify functional defects, inconsistencies, or unexpected behaviours affecting an application’s usability or performance. The app behaviour is analysed based on scenarios, boundary conditions, and valid or invalid inputs. 

One of the advantages of black box testing is that it gives testers the end-users perspective. They simulate real-world usage scenarios and validate the application’s functionality. Some black-box testing techniques include equivalence partitioning, error guessing, boundary value analysis, and decision table testing.

2. White box testing

White box testing is the analysis of the application’s internal structure and various components’ interaction with each other. Testers with various programming languages and coding principles can perform thorough tests to verify the application’s accuracy, completeness, and reliability. This technique allows for identifying code vulnerabilities, logical errors, and potential performance bottlenecks.

The benefits of white box texting include early bug detection, code optimisation, and enhanced test coverage. 

Here are some of the strategies for white box testing: 

  • Statement coverage ensures every code line is executed at least once during testing, verifying the basic app functionality. 
  • Branch coverage guarantees evaluating every possible decision point (branch) in the code, validating various execution paths and logical conditions.
  • Path coverage examines all possible paths through the application (loops and conditional statements) to verify the program’s behaviour under different scenarios.

3. Grey box testing

Grey box testing is a software testing approach combining black box testing elements and white box testing. Testers have limited, contextual knowledge of the application’s internal workings that aid their testing efforts. This partial insight enables them to design targeted test cases and uncover defects that (would) have gone undetected in black-box testing.

Grey box testing has several benefits, including improved test coverage, realistic test scenarios, and more efficient bug identification. It bridges the gap between black-box and white-box testing.

Testing levels

Various application testing levels also represent different stages of testing within the overall testing process or methodology. Each level focuses on specific aspects of the application and helps ensure its quality, functionality, and performance. They are as follows:

1. Unit testing

Unit testing is the first level where the smallest app code components or    even code units are tested in isolation, focusing on verifying the correctness of each unit. Test cases with boundary conditions and expected inputs/outputs are designed to cover different scenarios. Unit testing helps to determine bugs earlier in development and provides a solid foundation for the subsequent testing levels.

2. Integration testing

Integration testing comes after unit testing and focuses on integrating the application’s components or modules. It aims to uncover issues that may arise when combined units work together. Test cases are designed to verify the proper data flow, communication between components, and the integrated system’s overall functionality. Integration testing ensures that the components work cohesively and seamlessly as intended.

3. System testing

System testing is the highest testing level performed on the complete system or application. It verifies that integrated components function correctly and meets the specified requirements. This testing level examines the system from end to end, simulating various user scenarios and validating the software’s functionality, performance, and reliability. System testing is the final stage to ensure the application works as expected, meets user expectations, and is ready for deployment.

Challenges in application testing

Application testing is not always a hot knife through butter; it comes with several challenges. If you are going to thoroughly test your application, brace yourself for the following challenges:

  1. Building a perfect test environment: Creating and maintaining a suitable test environment that accurately represents the production environment requires much work. You should configure hardware, software, networks, and databases to closely mimic the real-world conditions in which the application will operate. 
  2. Test data management: Another challenge will be acquiring and managing realistic and diverse test data that covers various scenarios. You should be able to generate representative data without making it too specific to avoid the negative consequences of a potential leak. 
  3. Lack of time and resources: You often operate within tight schedules and limited resources during testing. You should be able to allocate sufficient time for thorough testing, secure appropriate test resources (such as tools, infrastructure, and skilled testers), and manage priorities to make the most out of them. 
  4. Complexity: Modern applications feature intricate architectures, integrations, and dependencies that are not simple to deal with. You should be able to ensure comprehensive testing coverage across these complexities and test the scalability and application performance for handling increased user loads. 
  5. Test case design: Application testing also requires designing effective test cases to cover all relevant scenarios and edge cases. You have to ensure sufficient coverage, prioritise tests based on risks, and maintain traceability between requirements and test cases. 
  6. Defect management: Efficiently tracking, reporting, and managing defects discovered during testing will require prioritising and resolving defects within specified timelines.  During this time, you should be able to coordinate with development teams effectively, using your best communication skills.
  7. Test automation: Implementing and maintaining automated test scripts can be difficult to apply to complex applications. It requires developing robust test scripts, managing test data, and ensuring the stability and maintainability of automated test suites.

Challenges in application testing

Best tool for application testing

So, how do you deal with these challenges? When testing applications, what should you do to complete your application testing perfectly, leaving no room for mistakes or delays? We suggest you try an all-in-one testing tool that meets all requirements of a modern software testing team. 

Introducing a perfect QA testing tool — aqua, an exceptional solution that offers comprehensive test management capabilities with a user-friendly and intuitive platform. With its AI-powered features, aqua cloud enhances testing efficiency, saving you valuable time and resources throughout testing.

One of this application testing software’s notable strengths is its focus on speed and security. The tool allows you to execute tests swiftly, reducing test cycle times and accelerating the testing process. By offering optional On-Premise or Custom Cloud deployment, aqua meets the needs of companies that work in regulated industries and sensitive markets.

aqua cloud also emphasises effective communication and collaboration among team members, enabling seamless sharing of test cases and results, facilitating better coordination and knowledge sharing within your team, and encouraging transparency. The simplicity of aqua cloud’s interface contributes to its user-friendly nature, making it accessible to both experienced testers and those new to the field. The workflows functionality helps you to guide new testers, while custom reports with KPI alerts are perfect for keeping your hand on the pulse.

Use the power of AI for fast and efficient application testing

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Now that you made it to the end of this comprehensive article, you have grasped what application testing is. You know the levels, the types, the challenges, and much more.,But application testing is more than just understanding the theory behind it; you should also be able to implement the strategies mentioned in this article. 

Good application testing means thorough testing, considering different testing categories, embracing automation and collaboration, and staying up-to-date with evolving practices. Doing so can enhance your applications’ quality, reliability, and success, ensuring customer satisfaction and business growth. Happy testing!

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What is the purpose of application testing in software development?

Application testing aims to ensure the developed software application’s quality, functionality, and reliability.

What are the different types of application testing, and what do they entail?

Here are the different types of application testing: 

  • Functional testing: Verifies if the application functions as intended
  • Non-functional testing consists of various testing types, including these: 
  1. Performance testing: Assesses the application’s speed, scalability, and responsiveness under different conditions 
  2. Security testing: Identifies vulnerabilities and ensures the protection of sensitive data 
  3. Usability testing: Evaluates the user-friendliness and intuitiveness of the application 
  • Regression testing: Ensures that changes or updates do not break existing functionality 
  • Acceptance testing: Validates if the application meets specified requirements and user expectations

A/B testing: Compares different application versions to determine performance or user preference

How do testing methodologies like black box, white box, and grey box testing differ from each other?

While black box testing focuses on external behaviour, white box testing delves into internal details, and grey box testing falls somewhere in between. The choice of methodology depends on the testing objectives, available information, and the level of detail required to uncover potential issues.

What tools are commonly used in application testing, and what are their specific functions?

Several tools are commonly used in application testing, each serving specific functions. Here’s a brief overview: 

  1. Test management tools (e.g., TestCollab, aqua cloud): Help in planning, organising, and tracking testing activities, including test case management, defect tracking, and reporting. 
  2. Automation testing tools (e.g., Selenium, Appium): Enable the creation and execution of automated test scripts. 
  3. Performance testing tools (e.g., Apache JMeter, LoadRunner): Assess the application’s performance, scalability, and responsiveness under various load conditions. 
  4. Security testing tools (e.g., OWASP ZAP, Burp Suite): Identify vulnerabilities, perform security scans, and protect sensitive data. 
  5. Code review tools (e.g., SonarQube, Crucible): Analyse code quality, detect potential issues and enforce coding standards.
  6. CI/CD tools (e.g., Jenkins, GitLab CI/CD): Facilitate automated building, testing, and application deployment.
What are some of the challenges faced during application testing, and how can they be addressed?

Here are some challenges in application testing and how you handle them: 

  1. Tight timelines: Prioritise critical functionalities
  2. Evolving technologies: Stay updated and adapt 
  3. Test environment and data management: Ensure suitable environments and manage test data 
  4. Communication and collaboration: Foster clear communication channels 
  5. Comprehensive test coverage: Prioritise based on risks 
  6. User experience testing: Incorporate usability testing
  7. Resource constraints: Optimise testing efforts
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