API testing is the process of validating application programming interfaces (APIs). The purpose of API testing is to verify the functionality, reliability, performance, and security of programming interfaces. API tests use software to call APIs, capture output, and record system responses instead of using standard user (keyboard) input and output.
What are APIs?
- API stands for Application Programming Interface. They are collections of functions and procedures that enable communication between two applications or libraries.
- This is one of the most difficult types of tests. Missing certain cases in API tests can cause major problems in production after full integration and can be difficult to debug in production.
What is API Testing & Types of APIs ?
- Check the key in the Min and Max API section.
- Create test cases to validate XML, JSON schemas, and key validation. If you’re using the JSON, XML API, you’ll need to check if all the keys come. Check the handling of API error codes.
- This definitive guide covers the REST API.
Various API types
- Rest APIs
- Soap APIs
REST is an acronym for Representational State Transfer. REST APIs should be tested for validation, error codes, and load testing. It provides a common interface for interaction and communication between the two systems.
REST APIs use the architectural style and it has 6 main constraints:
- Client Server
- Uniform Interface
- Layered System
- Code On Demand
REST API is developed by using these constraints.
- SOAP (Simple Object Access Protocol) is a messaging protocol that allows programs running on different operating systems or services, such as frontends and backends, to communicate via Hypertext Transfer Protocol (HTTP) and its Extensible Markup Language (XML).
- SOAP uses WSDL. WSDL is an XML format for describing network services as a set of endpoints, it operates on messages and contains document-oriented information.
- GraphQL reduces the gap between REST and SOAP. Therefore, it has some standardized rules, but still gives the freedom of REST APIs.
- GraphQL is a query language for APIs. It also executes those queries with your current data. GraphQL empowers clients to request only what they require, making it easier to evolve APIs over time and enabling powerful developer tools by providing a clear and comprehensible description of the data in your API.
What should be Tested in API tests?
- Validate keys with minimum and maximum API ranges.
- Prepares test cases for XML, JSON schema validation, and key validation. If you have a JSON, and XML APIs, you have to check that it includes all the keys. Find out how to handle API error codes.
Why should I do API testing?
- Many of the services we use on a daily basis rely on hundreds of interconnected APIs. The service will not function if it fails.
- There are millions of APIs in use on the internet today and they should be verified and tested.
- Sometimes, developers build broken APIs by mistake.
- Validating APIs before going into production is very important. Let’s have a look at the architecture of the application.
HTTP – Basic
- HTTP is an application layer protocol that was created as a part of the Internet Protocol Suite.
- I have a client that executes a request resource. This could be an HTML page, a server and additional files from the server.
- It uses the same protocol called HTTP to return the response to the client.
- HTTP is a stateless protocol. In other words. Therefore, the current request can not know about previous requests.
- What are Cookies?
Cookies are small text files that contain an ID tag and are typically saved in your computer’s browser directory or program data subfolder.
- What is Authentication?
Authentication is the process by which a credential or other private key is presented to a system and the system verifies it. In API terms, authentication can protect content on the Internet. Thus, only valid users with appropriate credentials can access this API endpoint.
HTTP Methods Explained
- GET – request to read data
- HEAD – request to read header data
- PUT – request to save data
- POST – attach to a name resource (e.g. web page)
- DELETE – delete data
- TRACE – Echo an incoming request
- CONNECT – Reserved for future use
- OPTIONS – query specific options
How can I test my API?
- A Postman is a tool you can use to test your API. Now run a simple API test.
- In Postman, go to your workspace. Click the + icon to open a new tab.
- Enter the API endpoint and method where it says “Enter the request URL” (action type GET, POST, etc.).
- Click on the send button
- GET REQUEST :
- As you can see in the image below, the response received from the API is displayed with a status of 200. This shows the successful request.
- For the Post method, you can also provide the request body in one of the listed formats.
- POST REQUEST :
- Select POST as the method and write the request URL. This example sends the request data in JSON format. For this option, you need to go to Body and select raw from the radio button list. Then select JSON.
- Compose the body of the request (you can enter headers as per your preference) and click on the send button.
- As you can see in the image below, a status 201 was received. This means the request was successful and the resource creation is completed. See Headers for API call details. You can also save the request by clicking the Save button to add it to Postman’s collection.
API Testing Tools
- Postman CI/CD
- Katalon using CI/CD
- SoapUI CI/CD
- Rest Assured CI/CD
API testing is a critical skill for testers in the world of the internet. Developers only test the features they are working on, whereas testers evaluate both individual features and sets or chains of features to determine how they interact from beginning to end.
This article has covered everything a beginner needs to know before diving into the world of API testing. You’ve learned the fundamentals of API testing, but there’s still a lot more to learn.
Happy API Testing Folks !!!