A reliable web app needs more than a check that its pages load. Test code units, connected modules, user-facing features, complete journeys, supported environments, performance, and security—and include accessibility and usability checks across those categories. There is no universal standard that fixes web app testing at exactly eight types: these eight are a practical selection, and a single test can fit more than one category.
What the eight types cover
The categories below describe different testing goals, not mutually exclusive phases. For example, a browser-based test might verify a feature end to end and be rerun later as regression coverage. Choose checks according to the behavior and risks you need to verify.
| Type | What it checks | Typical timing and method | Evidence and risks addressed |
|---|---|---|---|
| Unit | A small function, component, or other code unit in isolation. | During development; commonly automated. | Shows whether the isolated unit behaves as expected; can catch local logic errors. |
| Integration | Whether connected modules work correctly together. | When modules are integrated and in repeatable automated runs where appropriate. | Shows whether module boundaries and interactions behave as intended; can catch failures that isolated checks miss. |
| Functional | Whether app features behave as expected, including interactions, forms, navigation, and links. | During development and in regular automated or manual checks. | Records whether specified behaviors work; can catch broken controls, flows, and feature outcomes. |
| End-to-end | A complete user journey across the app’s relevant layers. | Often automated in a browser, including in CI where appropriate. | Shows whether the journey works as a whole; can reveal failures spanning multiple layers. |
| Regression | Whether existing behavior still works after a change or fix. | After changes and defect fixes; rerun relevant checks. | Provides evidence that a change has not broken previously working behavior. |
| Compatibility | Behavior across selected browsers, operating systems, and devices. | During development and before release, against an audience-based environment matrix. | Records behavior in tested environments; can catch browser- or device-specific problems. |
| Performance | Responsiveness, speed, scalability, and stability under different workloads. | During development and before release; measure against relevant workloads and hardware. | Produces measurements under specified conditions; can reveal slowdowns or instability, including on lower-spec mobile hardware. |
| Security | Whether security controls work and where the app has weaknesses. | As part of development and security review; test relevant app surfaces. | Findings identify weaknesses in controls, configuration, or application behavior. |
1. Unit testing: check a small piece in isolation
A unit test focuses on one small target, such as a function or component, rather than asking whether the whole app works. Use it for repeatable checks of local behavior, such as whether a function returns the expected result for defined inputs.
Unit tests help pinpoint a problem close to its source. They cannot, by themselves, establish that other modules, browsers, or complete user journeys work.
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2. Integration testing: check the connections
Integration tests examine whether modules work correctly together. They matter when behavior crosses a boundary—for example, when one component passes data to another or a feature depends on several connected parts.
A module can pass its isolated checks yet fail when connected to the rest of the app. Include integration checks where those interactions are important, rather than assuming unit coverage proves the connection works.
3. Functional testing: check features against criteria
Functional testing asks whether an app feature does what users and product requirements expect. Define the expected outcome first, then test interactions such as entering and submitting a form, following navigation, or opening a link.
Many functional checks are repeatable and can be automated. Others benefit from manual review, especially when the expected behavior depends on how people perceive or use the interface. The check should leave clear evidence of which behavior passed or failed.
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4. End-to-end testing: follow a whole user journey
An end-to-end (E2E) test follows a user journey through the relevant layers of the app. A journey might include navigating to a feature, entering information, submitting it, and checking the resulting state. Unlike a unit test, it checks that multiple parts work together from the user’s perspective.
Browser runners can automate suitable journeys, but no single E2E method fits every app. Keep these tests focused on important flows: a test that spans many components can expose system-level failures, but failures may require more investigation than a narrowly scoped unit check.
5. Regression testing: rerun checks after a change
Regression testing means rerunning relevant checks after a fix or other change to confirm that old behavior still works and the update has not introduced new errors. It is a purpose for running tests, not necessarily a separate technique: a unit, functional, or end-to-end test can all contribute to regression coverage.
After fixing a defect, rerun the check that exposed it and other checks likely to be affected by the change. Record the results so the team can see what was tested and what remains uncertain.
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6. Compatibility testing: check the environments your users rely on
Compatibility testing checks app behavior across a selected set of browsers, operating systems, and devices. The useful question is not whether the app runs on every imaginable configuration, but whether it works in the environments relevant to its intended users.
Identify those users and build a practical test matrix from the browsers and devices they use. Testing on a physical phone can reveal mobile layout and touch issues that a desktop browser alone may not show; one phone, however, does not validate every device or browser.
7. Performance testing: measure speed and stability
Performance testing measures responsiveness, speed, scalability, and stability under different workloads. Choose conditions that reflect the app’s use, and interpret each result in the context of the workload and hardware used.
Consider lower-spec mobile hardware when performance-sensitive behavior matters. A result from one machine or workload does not establish how the app performs under every condition.
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8. Security testing: examine controls and weaknesses
Security testing evaluates whether an app’s security controls work and identifies weaknesses. The OWASP Web Security Testing Guide organizes coverage into areas including configuration, identity, authentication, authorization, session management, input validation, error handling, cryptography, business logic, client-side testing, and APIs.
Use those areas to think through which parts of the app need review; security is broader than checking a login screen. OWASP’s project page lists WSTG 4.2 as the latest versioned release and says 5.0 is under development; version status can change, so consult the OWASP Web Security Testing Guide project page for current details.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Accessibility and usability belong across the test plan
Accessibility and usability are essential, even though they are not separate entries in this eight-item selection. Accessibility checks whether people with disabilities can use the app; usability evaluation examines how people complete tasks and understand the interface. These concerns cross feature, compatibility, and end-to-end testing rather than fitting neatly into one test level.
W3C WAI explains that “All WCAG 2 success criteria are written as testable criteria for objectively determining if content satisfies them.” It also describes evaluation as a combination of automated testing and human evaluation. Automated checks can help identify issues, but they do not establish that an app is usable for people with a wide variety of disabilities. Involve people in usability evaluation, including participants with disabilities when assessing accessibility, and consider keyboard, touch, readable text, and assistive technology behavior.
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For broader or formal evaluation, the W3C WCAG Evaluation Methodology (WCAG-EM) 2.0 discusses evaluation approach and representative sampling. Passing success criteria alone is not a guarantee of usability.
How to build a practical web app test workflow
- Identify the audience and environments. Decide which user groups the app serves and which browsers and devices they use. Use that information to choose a compatibility matrix rather than aiming to cover every possible environment.
- Write acceptance criteria before testing. Specify visible behavior and expected outcomes. Where relevant, include keyboard and touch interaction, readable text, and assistive technology behavior.
- Choose test categories by feature and risk. Use unit checks for isolated logic, integration checks at important module boundaries, and functional or end-to-end checks for user-visible behavior and journeys. Add performance and security work where the risks call for it.
- Automate repeatable checks and run them regularly. Run appropriate tests after code changes or through continuous integration (CI), and document the results. Keep manual checks for questions that automation does not answer.
- Evaluate usability and accessibility with people as well as tools. Combine automated checks with human evaluation. Include users with disabilities in usability studies where appropriate.
- Rerun checks after fixes. Verify the repaired behavior and review relevant coverage for regressions; preserve a record of what was rerun.
Choosing testing tools without overcommitting
Google’s frontend testing guidance names Jest, Vitest, Cypress, Mocha, and Jasmine as framework examples, and Web Test Runner, Playwright, WebDriver, and Node.js’s Test Runner as runner examples. MDN gives CircleCI and Travis CI as examples of CI services. These are examples, not a ranking or a claim that every tool suits every app.
Compare tools by the language and browser environment they support, the target they test, whether they fit your CI setup, and how maintainable their tests are. Tool choice does not remove the need for real-device checks where devices matter, or human accessibility and usability evaluation where the question involves people’s experience.
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