Web app testing: 8 essential types

Testing is a crucial step in web application development. It ensures that web apps function properly, remain secure, and deliver a seamless user experience.

In fact, skipping this step can lead to bugs, performance issues, and security vulnerabilities that expose user data and harm your reputation. To avoid these risks, you should learn how to test your web app before deployment.

In this guide, we’ll explain the key types of web app testing, share practical tips, and recommend tools to streamline the testing process. By the end, you’ll be fully able to test a web application, whether you’re launching a new app or improving an existing one.

What is web application testing?

Web application testing is the process of evaluating a web app’s functionality, performance, and security based on quality standards. This helps identify issues, such as broken features, poor user interface (UI) design, slow server response times, and weak authentication, before releasing the app to users.

For quality assurance (QA) testers, web app testing can catch problems early, improve stability, and help avoid costly fixes after deployment. As a result, the application will meet functional requirements, work across different devices and browsers, and handle unexpected traffic without crashing.

The web app testing cycle typically follows these stages:

1. Test planning – define testing objectives, scope, and strategy.
2. Test case design – create detailed test cases based on app requirements and expected behavior.
3. Test environment setup – prepare tools, devices, and configurations needed for testing.
4. Test execution – run test cases, detect issues, and report findings.
5. Bug fixing – collaborate with developers to resolve identified issues.
6. Re-testing and regression testing – verify fixes and check that new changes don’t break existing features.
7. Test closure – analyze results, document lessons learned, and prepare for deployment.

How to test a web application

Before testing a custom web application, make sure you have developed all the desired features, whether through manual coding with programming languages and frameworks or using AI-based tools like Hostinger Horizons, which lets you build a functional web app by simply entering prompts.

Next, set up a dedicated testing environment that mirrors your production setup. This involves configuring servers, databases, and external services your app relies on. Use containerization tools like Docker to maintain consistency across different testing stages.

Then, select the right testing tools based on the test types you’ll perform. We’ll cover these tools later in this article.

Once everything is in place, test your web app with different test types. Each type focuses on a specific area to ensure a thorough evaluation.

1. Functionality testing

Functionality testing ensures that a web application’s core features work as expected. This test type verifies that key components, such as user registration, login/logout, form submissions, and page navigation, perform correctly under different conditions.

It helps identify broken features, logical errors, and inconsistent behaviors within the app.

How to run a functionality test

1. Define test scenarios – create detailed scenarios for key features. Each scenario should specify inputs, expected results, and steps to execute the test.
2. Perform manual or automated tests – manually test simple features like form validation or navigation. Use automation tools like Selenium for repetitive tasks, such as login/logout and data entry.
3. Ensure proper error handling – simulate errors, such as entering incorrect login credentials, to confirm that the app handles errors without crashing.
4. Track and document defects – record issues, categorize their severity, and monitor their resolution throughout the testing process.

Key metrics to track

• Test coverage – the percentage of app features covered by tests.
• Defect rate – the number of defects or failed tests detected.
• Number of successful test cases – the total number of test cases that pass without errors.

Best practices for usability testing

• Prioritize high-risk features – focus on critical functions first, such as user authentication and payment processing.
• Check UI responsiveness – verify that all UI elements work correctly across various devices and screen resolutions.
• Test workflows end-to-end – simulate real user actions to verify that complex workflows, like purchases or multi-step forms, run smoothly.

2. Usability testing

Usability testing evaluates how easily users can interact with a web application. The goal is to ensure a smooth, intuitive experience by identifying and fixing problems like confusing navigation, inconsistent design, and hard-to-read text.

Conducting usability testing can improve user satisfaction, enhance overall app usability, and ensure compliance with the Web Content Accessibility Guidelines (WCAG).

How to run a usability test

1. Define test objectives – identify the specific areas you want to evaluate, such as navigation flow, form completion, or accessibility compliance.
2. Involve real users – run test sessions with individuals from your target audience. Observe their behavior as they complete predefined tasks.
3. Collect and analyze feedback – use tools like Hotjar or Maze to gather insights through heatmaps, session recordings, and surveys. Focus on areas where users struggle or abandon tasks.
4. Analyze user behavior – record how users interact with your web app. Identify pain points like navigation difficulties or unclear instructions and prioritize improvements based on feedback.

Key aspects to focus on

• Task success rate – the percentage of users completing a specific task successfully.
• Time on task – how long it takes users to complete tasks like filling out a form or making a purchase.
• WCAG compliance – make sure your web app is accessible to everyone, including users with disabilities. Provide proper color contrast, keyboard navigation, and a screen reader.

Best practices for usability testing

• Involve diverse users – include participants with different backgrounds and abilities for well-rounded feedback.
• Keep the test environment natural – let users explore your web app freely while completing specific tasks.
• Observe without interfering – avoid guiding users during tests. Let them figure things out independently to uncover real usability issues.
• Test across multiple devices – ensure a consistent experience on desktops, tablets, and mobile devices.

3. Interface testing

In interface testing, you verify interactions between different web application components, such as the front end, web server, database, and third-party services like APIs.

This test can help detect data mismatches, transfer failures, module integration issues, and incorrect API responses. It ensures accurate data flow and seamless communication across all components.

How to run an interface test

1. Identify key interfaces – list all interfaces your application uses, including internal APIs, external services, and database connections.
2. Define test cases – identify possible interactions between modules, such as retrieving data from APIs or updating the database after user input.
3. Assess data transfer – make sure that data transfers correctly between components. For example, verify that user-submitted information on the front end appears accurately in the database.
4. Verify error handling – simulate errors by sending invalid API requests or disconnecting from the database. Confirm that the system handles them gracefully with appropriate error messages.

Key aspects and metrics to focus on

• UI consistency – the uniformity of the user interface across different modules and interactions.
• Data transfer accuracy – the percentage of data transferred correctly between components.
• Response time – the time it takes for a module to respond to a request.
• Error rate – the frequency of errors occurring during communication between modules.

Best practices for interface testing

• Automate repetitive tests – use tools like SoapUI or Postman for faster and more reliable testing of API responses and data validation.
• Test for edge cases – include extreme scenarios, such as high server load, incomplete data, or failed external services, to confirm system stability under different conditions.

4. Database testing

Database testing assesses the database layer of a web application so that all operations, such as storing, retrieving, and updating data, are accurate and efficient.

This type of testing helps identify data corruption, incorrect table relationships, slow or ineffective queries, and vulnerabilities like SQL injection. By thoroughly testing the database, you can confirm that your web app stores and retrieves data exactly as users input it.

How to run a database test

1. Verify CRUD operations – test Create, Read, Update, and Delete (CRUD) operations to ensure proper data handling. For example, check that user registration adds a new record to the database and that updating profile information modifies the correct fields.
2. Perform data validation – make sure that data meets expected formats like numeric values and date formats. Verify that proper error messages appear when validation fails.
3. Check database constraints – test primary keys, foreign keys, and unique constraints to maintain data integrity and prevent duplication.
4. Test indexing and query performance – measure query response times using complex queries, like multi-table joins and nested queries, to assess performance and data retrieval.
5. Assess data security – simulate SQL injection attacks to verify the database is safe from unauthorized access.

Key metrics to track

• Data accuracy – the percentage of records that match expected values.
• Data discrepancies – the frequency of inconsistencies found between related tables.
• Query response time – the average time the database takes to execute queries.

Best practices for database testing

• Use automation tools – automate routine tasks with tools like DbFit or SQL Server Management Studio (SSMS) to speed up validation and reduce errors.
• Test large data sets – simulate real-world data loads to confirm that the database performs well under high traffic and large data volumes.

5. Compatibility testing

Compatibility testing confirms that a web app works across different browsers, devices, operating systems, and screen resolutions. Since web browsers use different rendering engines and devices have varying hardware and OS behaviors, this test helps prevent unexpected issues.

In contrast, skipping compatibility testing can result in layout distortions, broken interactive elements, or inconsistent font rendering, which can frustrate users and drive them away.

How to run a compatibility test

• Define test environments – identify the browsers, operating systems, and devices your target audience uses the most.
• Perform cross-browser testing – use tools like BrowserStack or Sauce Labs to check how the app behaves in browsers such as Chrome, Firefox, Safari, Edge, and Opera.
• Test responsiveness across screen sizes – verify that UI elements adjust correctly across different screen resolutions, from desktops to mobile devices.
• Evaluate device compatibility – test the app on real devices and emulators to ensure smooth functionality across Android, iOS, Windows, macOS, and Linux.
• Check for feature support – some older browser versions may not support modern CSS, JavaScript, or API functions. Use browser developer tools to detect and resolve these issues.

Key metrics to track

• Browser coverage rate – the percentage of supported browsers that render the app correctly.
• Device compatibility success – the percentage of tested devices where the app functions without major issues.

Best practices for compatibility testing

• Prioritize testing for popular browsers and devices – use analytics to determine which platforms your users access the most.
• Test both new and legacy browser versions – maintain backward compatibility for users still using older browsers.
• Use emulators and real devices – emulators are great for quick checks, but real device testing provides the most accurate results.
• Regularly update test environments – as browsers and OS versions evolve, update your testing environments to catch new compatibility issues.

6. Performance testing

As the name suggests, performance testing evaluates how well a web application performs under different conditions, including regular and peak traffic periods.

By identifying scalability limits, resource bottlenecks, and slow response times, this test ensures the app can handle high user loads and process requests efficiently without slowdowns or crashes.

How to run a performance test

1. Define performance goals – set benchmarks for response time, server resource usage, and maximum concurrent users based on application requirements.
2. Use load testing tools – tools like Apache JMeter, Gatling, or Locust simulate high traffic loads and measure performance metrics.
3. Run different types of performance tests:
   • Load testing – simulates normal and peak user traffic to assess the app’s performance under expected loads.
   • Stress testing – pushes the system beyond normal capacity to determine its breaking point.
   • Scalability testing – evaluates how well the app adapts when additional users or resources are added.
4. Monitor system resources – track CPU, memory, and bandwidth usage during testing to detect potential overloads.

Key metrics to track

• Response time – the time the server takes to process and respond to a request.
• Number of concurrent users – the maximum number of users the app can handle simultaneously without performance degradation.
• Error rate under load – the percentage of failed requests when the system is under heavy traffic.

Best practices for performance testing

• Combine performance and functionality testing – make sure that all core features work as expected under load.
• Optimize based on findings – use profiling tools like New Relic or Datadog to pinpoint inefficient code, slow queries, and resource-heavy processes.
• Continuously monitor performance – implement real-time performance tracking to detect slowdowns before they impact users.

7. Security testing

Security testing identifies vulnerabilities in a web application and ensures that sensitive information remains protected from cyber threats. It helps prevent unauthorized access, data breaches, cross-site scripting, and injection attacks.

By proactively testing for vulnerabilities, you can strengthen authentication, authorization, and data encryption mechanisms, reducing risks that could lead to financial loss, legal consequences, or reputational damage.

How to run a security test

1. Identify security requirements – define which security aspects need testing, such as user authentication, data access controls, and encryption protocols.
2. Use security testing tools – ZAP, Burp Suite, and Nikto can scan for vulnerabilities such as SQL injection, cross-site scripting, and security misconfigurations.
3. Run penetration tests to identify manually:
   • SQL injection (SQLi) – exploits weak database queries to access or modify sensitive data.
   • Cross-site scripting (XSS) – injects malicious scripts into web pages viewed by users.
   • Cross-site request forgery (CSRF) – tricks users into performing unintended actions.
4. Test authentication and authorization – make sure that password policies, multi-factor authentication (MFA), and role-based access control (RBAC) function correctly.
5. Check data encryption – confirm that sensitive data is encrypted during transmission and storage using Transport Layer Security (TLS) and AES encryption.
6. Review security headers and configurations – verify that Content Security Policy (CSP), HTTP Strict Transport Security (HSTS), and Cross-Origin Resource Sharing (CORS) are properly implemented to prevent common exploits.

Key metrics to track

• Number of vulnerabilities – the total number of security flaws detected during testing.
• Severity of risks – the impact level of each vulnerability, categorized as low, medium, high, or critical.
• Response time to fix issues – the time taken to patch and mitigate identified vulnerabilities.

Best practices for security testing

• Integrate security testing into the development cycle – use DevSecOps practices to test security continuously.
• Regularly update security tools and libraries – outdated dependencies can introduce vulnerabilities.
• Educate the development team – train developers on secure coding practices to minimize risks from the start.

8. Crowd testing

Crowd testing involves external testers, often from different locations, devices, and networks, to evaluate a web application under real-world conditions.

This approach helps uncover bugs and usability issues that might not appear in controlled testing environments. It provides diverse feedback on functionality, performance, and cross-device compatibility, ensuring a better user experience across multiple platforms.

How to run crowd testing

1. Define testing objectives – identify the key aspects of the web application to test, such as functionality, usability, performance, or security.
2. Choose a crowd testing platform – use platforms like Test.io, uTest, or Applause, which connect businesses with professional testers worldwide.
3. Recruit diverse testers – include participants from different geographic locations, technical backgrounds, and device preferences to maximize test coverage.
4. Distribute test scenarios – provide structured test cases, such as testing form submissions, evaluating UI responsiveness, and assessing performance under unstable internet connections.
5. Collect and analyze feedback – gather tester reports on bugs, usability issues, and performance concerns using detailed logs, screenshots, and screen recordings.

Key aspects and metrics to focus on

• Bug discovery rate – the number of issues found per testing cycle.
• Test scenario diversity – the variety of test cases executed across different browsers, devices, and environments.

Best practices for crowd testing

• Combine exploratory and structured testing – let testers freely explore the app while following predefined test scenarios.
• Encourage detailed reporting – ask testers to provide screenshots, logs, and step-by-step bug reports for clarity.

Helpful tools to test your web application

Below is a curated list of testing tools categorized by their primary function:

Automated testing tools

• Selenium – automates tests across multiple browsers and platforms. It supports various programming languages, including Java, Python, and C#.
• Katalon Studio – an automation tool for web, API, and mobile testing. Its intuitive interface makes it suitable for both beginners and advanced testers.

Security testing tools

• Zed Attack Proxy (ZAP) – detects security vulnerabilities in web applications during development and testing.
• Burp Suite – helps map, identify, and exploit security vulnerabilities in web applications.

Code quality testing Tools

• SonarQube – continuously inspects code quality, detecting bugs, vulnerabilities, and code smells across multiple programming languages.
• ESLint – identifies problematic patterns in JavaScript, helping maintain code quality and consistency.

Load testing tools

• Apache JMeter – tests functional behavior and measures performance. It supports both static and dynamic resources.
• OpenText Professional – predicts system behavior and performance, helping detect and resolve potential issues before deployment.

Usability testing tools

• UserTesting – provides real-time video feedback from users interacting with your application, offering insights into user experience.
• Lookback – a platform for user research, supporting live interviews and self-guided tests while capturing user interactions and feedback.

Cross-browser testing tools

• BrowserStack – enables testing of web applications across various browsers and devices without requiring local setups.
• LambdaTest – provides a scalable cloud infrastructure for real-time cross-browser testing, ensuring compatibility across different browser versions and devices.

Conclusion

Web application testing ensures your app is reliable, secure, and high-performing across different environments. By conducting proper testing, you can detect and fix issues early, preventing performance bottlenecks, security vulnerabilities, and compatibility problems.

In this guide, we’ve covered the key types of web application testing, from functionality and compatibility checks to security assessments. Choosing the right testing methods and tools will help you build a web application that meets industry standards and user expectations.

After thoroughly testing your web app, it’s time to deploy it to a server so it’s live and ready for visitors. After launch, promote your web app to attract more users and grow your audience.

If you have questions about web application testing, feel free to ask in the comments below!

Web app testing FAQ