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This article outlines everything you need to know about API Testing. We also provide answers to key interview questions so you can be fully prepared for tomorrow’s interview.

API Testing is a process that ensures that the software works as intended. These interviews are used to determine the candidate’s knowledge of API Testing, their experience with testing and what they would do in various situations.

Let’s get started with API Testing Interview Questions!

What is an API?

An API (Application Programming Interface) is a software intermediary that enables two applications to communicate with each other. It comprises a number of subroutine definitions, logs, and tools for creating application software. In an API testing interview, you could be asked to give some API examples, here are the well-known ones: Google Maps API, Amazon Advertising API, Twitter API, YouTube API, etc 

What is API Testing?

API testing is the process of testing an API to see if it functions as expected. It is done by using a tool called Postman, which simulates requests and responses. 

What is Payload in API Testing?

API testing is the process of testing an API to see if it functions as expected. It is done by using a tool called Postman, which simulates requests and responses. 

What is API Testing?

Payload is the data that is carried in a message. It can be anything from a JSON object to an XML document to text or binary data. Payload-specific commands can be used to parse the payload and alter its contents based on prior knowledge. 

What is API Documentation?

The API documentation is a complete, accurate technical writing giving instructions on how to effectively use and integrate with an API. It is a compact reference manual that has all the information needed to work with the API, and helps you answer all the API testing questions with details on functions, classes, return types, arguments, and also examples and tutorials 

What is a “Resource” in REST? 

REST architecture treats any content as a resource, which can be either text files, HTML pages, images, videos or dynamic business information. REST Server gives access to resources and modifies them, where each resource is identified by URIs/ global IDs

What is the most popular way to represent a resource in REST?

REST uses different representations to define a resource like text, JSON, and XML. XML and JSON are the most popular representations of resource. 

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API Testing Interview Questions

What are the different ways to test an API?

There are many ways to test an API. Some of them are:

-Unit tests

-Integration tests

-End-to-end tests

-Acceptance tests

-Load testing

-Runtime/ Error Detection

-Security testing

-Penetration testing

-Fuzz testing

What is the procedure to perform API testing?

  • Choose the suite to add the API test case
  • Choose the test development mode
  • Demand the development of test cases for the required API methods
  • Configure the control parameters of the application and then test conditions
  • Configure method validation
  • Execute the API test
  • Check test reports and filter API test cases
  • Arrange all API test cases

How can I properly test an API?

Testing an API is a very important part of the development process. It ensures that the API is working as expected and provides a safety net for when there are any bugs in the code.

There are various ways to test an API, but most of them require some level of programming knowledge. The easiest way to test an API is by using cURL commands through your terminal.

What are the design principles for an API testing?

The five most important API test design principles are as follows:

  • Setup: Create objects, start services, initialize data
  • Execution: Steps to use the API or run the scenario, including logging
  • Verification: Oracles will assess the execution’s outcome.
  • Reporting: successful, unsuccessful, or blocked
  • Cleaning: Pre-test state

What’s the distinction between SOAP and RESTful?

SOAP (Simple Object Access Protocol) :

  • SOAP is a protocol for exchanging XML documents between two computers.
  • Only the XML format is supported by SOAP.
  • Caching is not supported by SOAP.
  • SOAP is more time-consuming than REST.
  • SOAP is similar to a custom desktop application linked to the server.
  • SOAP uses HTTP, but it encapsulates the message.

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  • REST is a network-based software architecture service architecture and design.
  • REST accepts a variety of data formats.
  • Caching is supported by REST.
  • REST is more efficient than SOAP.
  • The REST client is similar to a browser in that it uses standard methods. It must be able to accommodate an application.
  • HTTP headers are used by REST to store metadata.

What are different types of Methods in API Testing?

  • GET: This method is used to request data from a given resource.
    It is possible to cache and bookmark GET requests. It is saved in the browser history and is limited in length. GET requests should not be used when dealing with sensitive data. 
  • POST: It is a method of sending data to a server to create r update resources.
    POST requests are never cached or saved in the browser. 
  • PUT: It replaces the target resource’s current representation with the request payload. 
  • DELETE: This command deletes the specified resource. 
  • OPTIONS: This word describes the target resources’ communication options. 
  • HEAD: It requests the same response as GET requests, but without the response body.

How do the PUT and POST methods differ?

There’s a lot of confusion when it comes to using the PUT and POST methods. Our goal with a POST request is to create a new object on the server, whereas a PUT request replaces an existing object with another.

POST should be used when a client sends a page to the server, and the server then tells the client where it went. The PUT command should be used when the client specifies the page’s location.

What is the caching mechanism?

Caching is just the practice of storing data in temporarily and retrieving data from a high-performance store (usually memory) either explicitly or implicitly. When a caching mechanism is in place, it helps improve delivery speed by storing a copy of the asset you requested and later accessing the cached copy instead of the original

How often are the APIs changed and, more importantly, deprecated?

APIs, especially modern RESTful APIs, are a nice creation that can certainly simplify and accelerate integration efforts, which makes it more likely you will benefit from them. But APIs can and do change for various reasons, sometimes abruptly, and hence REST APIs do not differ from traditional integration methods in this respect. If an API call is obsolete and disappears, your procedure will interrupt and it is important to understand how often the APIs you depend on change or are deprecated

What is the upper limit for a payload to pass in the POST method?

appends data to the service URL. But its size shouldn’t exceed the maximum URL length. However, doesn’t have any such limit. So, theoretically, a user can pass unlimited data as the payload to POST method. But, if we consider a real use case, then sending POST with large payload will consume more bandwidth. It’ll take more time and present performance challenges to your server. Hence, a user should take action accordingly

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