Benefits of API Testing in Software Development

Evgeniy Brik

Evgeniy Brik

Head of QA at Andersen

Quality Assurance
Apr 14, 2021
8 minutes to read
  1. What API is
  2. The essence of API testing
  3. The difference between API testing and GUI testing
  4. What API testing services include
  5. <em>Integration testing</em>
  6. <em>Functional testing</em>
  7. <em>Security testing</em>
  8. <em>Load testing</em>
  9. Benefits of API testing
  10. <em>1. Finding bugs at an early stage of software development</em>
  11. <em>2. Effective use of time</em>
  12. <em>4. Non-attachment to programming languages</em>
  13. <em>5. Improved test coverage</em>
  14. The future of automated API testing

Consumer orientation has changed the structure of software. Modern applications are scattered across mobile devices and web browsers, so users can access services anytime and anywhere. In addition, applications are no longer self-contained. They are made up of multiple service components that are linked at runtime. How does an application programming interface, or API, affect the interaction with the end user? And why is API testing becoming a normal practice for IT companies that provide quality assurance services? Let's try to figure it out.

What API is

API is a set of tools, using which one program can exchange data with another. This approach facilitates communication between modules, applications, and back-end systems. API testing helps specialists to promptly know when something goes down and fix the problem before users notice any inconsistency.

Simplistically, the performance of an API can be compared with taking an order in a cafe. A visitor selects a dish from a menu and sends their request to the kitchen via a server. The server, in turn, gives the task to the chefs and returns to the visitor with a plate of cooked food. Here, the server acts as an API, connecting one program (the visitor) to another (the kitchen).

A typical application has three distinct layers: the presentation (or user interface - UI) layer, the business layer, and the database layer for modeling and managing data. As you can see in the picture below, an API focuses on business logic. alt text An example of APIs in action is booking tickets online using a credit card. The bank provides an API for online transactions that are invoked by the flight booking website. The website sends a request and receives a response. Based on the response - 'Transaction was successful' or 'Unsuccessful transaction attempt' - the ticket is either booked or not. If the bank’s API doesn’t work, users can’t conduct financial transactions, which leads to profit losses and damage to the business’s reputation.

In applications, APIs are typically used to provide continuous communications between various software components, integrating them into a robust system.

The essence of API testing

Since we have figured out what an API is, it becomes obvious that API testing checks whether an API operates correctly. This process helps to ensure that performance, functionality, security, and reliability of software meet expectations - in other words, that the server (API) is able to serve several visitors simultaneously, return to the client, bring the exact dish that was ordered, and so on.

Consequently, ineffective APIs can result in integration difficulties, poor software quality, user frustration, and revenue losses. According to State of the Internet - a report by Akamai, API calls account for 83% of all web traffic. Quality assurance engineers perform automated API testing by using specialized software, which significantly simplifies and speeds up the checking process.

The difference between API testing and GUI testing

Testing of a GUI (graphical user interface) focuses on the appearance of a web interface. For example, it checks whether a certain payment button works, whether the menu is functional, whether the necessary fonts are used on the page, and so on. Application GUI checks will always be a necessity, but sometimes, finding the cause of the problem with their help is difficult. In the world of Agile methodologies, GUI testing is no longer enough.

API testing helps specialists dig deeper by focusing on the business logic layer of software architecture. The business layer is the most important - this is where all transactions between the UI and the database layer take place. API testing focuses mostly on using software to send API calls, get output, and log system responses, as well as on ensuring data security and software performance. alt text Moreover, testers can start testing APIs at an earlier stage of development. And the sooner the problem is dis