Testing is a crucial part of the software development life cycle. It helps ensure that software works as intended and meets user expectations. There are two main types of software testing - API testing and UI testing. Understanding the differences between doing API tests and UI testing can help developers choose the right testing strategy to build robust, failure-resistant software.
API stands for Application Programming Interface. APIs allow different software systems to communicate with each other by exposing some functionality. For example, the Twitter API allows other applications to connect with Twitter and get data like tweets, users, trends etc.
API testing is the process of testing API endpoints directly, with automated tests focusing on input and output of APIs. The aim of API testing is to validate that the APIs meet their design specifications and perform as intended.
Some examples of what API testing covers:
API testing is performed at the backend of a software without having a UI frontend. Test cases directly call the API endpoints and validate the responses.
UI stands for User Interface. UI testing focuses on testing the graphical user interface of an application from an end user's perspective. The aim ui tests is to ensure that the UI allows users to effectively use the software and behaves as designed.
Some examples of what UI testing covers:
UI testing process replicates real user interactions like clicking buttons, entering data in forms, navigation etc. It validates that the UI responds correctly to user actions.
API Testing | UI Testing |
---|---|
Tests backend application logic |
Tests frontend UI |
Focuses on input/output of API endpoints |
Focuses on look, feel and behavior of UI |
Validates functionality and design of APIs |
Validates functionality and design of UI |
Tests APIs independently without UI |
Tests UI as an end user would |
Automated using API testing tools |
Automated using UI testing tools |
Requires API level access |
Requires application front end access |
API testing and UI testing address different aspects of the user interface testing an application. Both API testing and UI testing are equally important for comprehensive testing.
Here are some factors that determine which kind of test scenarios of testing should be emphasized:
So in summary, the testing strategy should consider the context, priorities and type of system being tested. A balanced mix of both manual API testing and UI testing is ideal for most software projects.
Level 3 Communications was one of the largest telecommunication companies that filed for bankruptcy in 2014, after an failed effort to integrate and upgrade its billing systems led to turmoil. Customers were billed incorrectly, couldn't view or pay bills online and service was disrupted. So what went wrong and could API or UI testing have prevented this failure?
Level 3 had multiple billing systems for various services they acquired over the years. To simplify operations, they decided to consolidate all these into one unified billing system.
Here are some key pain points and limitations that led to the massive failure:
In summary, Level 3 failed to realize the enormity of the change and did not test the integrated systems thoroughly before launch.
More rigorous API testing could have mitigated some of the integration issues:
Improved UI and automated testing, of the customer portal and internal tools could have averted customer facing failures:
The poor API and UI testing rigour contributed significantly to Level 3's billing system meltdown. Extensive testing of the interfaces and full-stack functionality could have reduced overall technical and business impact.
Level 3's story exemplifies that complexity often leads to inadequately tested systems prone to failure. So how can organizations avoid such issues?
Here are some key lessons on integrating API and UI testing:
By combining API and UI with automated testing tools, organizations can deliver robust software that meets customer expectations even as complexity increases.
API testing and UI testing are complementary disciplines that jointly improve software quality and user experience. API testing focuses on validating application logic and backend functionality. UI testing replicates user workflows and verifies front end behavior.
To prevent epic failures like Level 3's billing system meltdown, companies need to emphasize both API and UI testing especially during integrations. Testing the entire system including interfaces early and often is the best way to de-risk complex changes. With cloud platforms making testing economical and more flexible, the ROI of rigorous test automation continues to grow.
As complexity explodes with technologies like cloud, IoT, AI and microservices, testing will prove pivotal in building resilient software that exceeds customer expectations. Organizations that skimp on testing do so at their own peril. Companies like Worksoft provide automated testing solutions to enable comprehensive and economical test coverage for complex business applications.
The main difference is that UI testing validates the graphical front end of an application while API testing focuses on testing backend APIs.
Usually UI testing finds more visual and usability defects while API testing finds more functional defects. Both testing tools and types are essential for comprehensive coverage.
API testing generally requires technical expertise to send requests and write test cases. UI testing has lower barrier to entry than api testing tools but can get complex for advanced UI flows.
It's good to start API testing in the initial stages of development as the backend gets built. UI testing can begin as stable UI becomes available.
Yes, both API testing and UI testing can be effectively automated using commercial and open source test automation tools and frameworks.
1 Federal Communications Commission, Level 3 Nationwide Outage Report, March 2018