API Testing

The main task of API testing is to check the functionality and security of the APIs and to see how all the system elements interplay end to end. We use Python and Robot Framework for API testing automation.

What exactly is tested?

  • possible input combinations;
  • response-related parameters (status codes, response body, the response by request parameters);
  • output parameters (whether the output is well-structured and appropriate for other applications);
  • API behavior in case of invalid requests;
  • authentication on the endpoints;
  • API performance (e.g. how much time the API is taking to retrieve data);
  • API security.

The main benefits of API testing

Early Testing

benefits of API testing.jpgAPI testing can be run simultaneously with back-end development so you can check the business logic and overall state of the application before starting working on front-end. Thus, some bugs can be detected at early stages of project development, before they become a more serious issue during the GUI testing.

Swift feedback

Sometimes functional GUI tests may be too slow to provide you with instant feedback. Automated API tests are way faster than browser tests and much easier to maintain.

As an example, the API layer can be tested immediately after some changes are made in business logic and so we may let the developers know about new bugs and regressions. In contrast, end-to-end testing takes up to several days.


By having detected issues at early stages you avoid expensive bug fixing at the release stage. Moreover, with our API testing framework, you can reduce manual testing or even some front-end testing needs.


Performing functional tests only isn’t enough to find vulnerabilities. API tests also cover a number of security-related issues.

A good example is trying to access authorized endpoints without authentication or with incorrect tokens and credentials. If your API exposes any sensitive data, you need tests that can simulate these kinds of attacks, unauthorized access, sending inputs of incorrect type or size, etc.

Easy Integration

Our API tests presuppose third-party integrations, which would mean the possibility of testing the third-party services that use the API in question. This way, our tests allow making sure the proper work of both the API and the interaction of any third-party applications with it. Types of interaction that can be tested in this manner include sending proper requests and returning corresponding data. This process is known as acceptance testing. Additionally, we provide integration with functional GUI tests in case these third-party services have a user interface.


Since API tests provide access to the application without a user interface, they are considered to be the best solution for the applications which are not meant to have a user interface or for those which need to be tested long before the front-end development starts.

If you’d like to learn more about this service or get a quote, all you need to do is to fill in this form.

Connect with our experts Let's talk