Best 40 API Testing Interview Questions

Here you will find “Rest sure API testing interviews questions” and the questions you need to prepare for the interview. The questions below are taken from the top test experts to prepare you to take on a new position.

Table of Contents

What exactly is REST?

Ans.  REST refers to Representational State Transfer. It is an architecture way of web-based services that benefit from the widespread use of the HTTP protocol and utilizes the HTTP protocol for defining actions. It is built around resources which is the term used to describe an element that is accessible via an open interface that uses HTTP common methods.

In the REST design, the REST Server gives access to resources, while the REST client is able to access and display the resources. Every resource is identified using URIs and global IDs. REST utilizes different methods to represent resources, including texts, JSON, and XML. XML, as well as JSON, represent the majority of well-known representations of resources today.

What is the most popular Method Of Representing the Resource in REST?

Ans.  REST uses different representations of resources such as JSON, text JSON, or XML.

JSON is one of the most well-known representations of resources.

What is a “Resource” For REST?

Answer. REST architecture considers every piece of content resource. These resources could be text files HTML webpages, photos videos, or even the dynamic data of business.

REST Server gives accessibility to the resources while the REST Client allows and modifies the resources. Every resource is identified with URIsor global IDs.

Which Protocol is used by the RESTful Web Services?

Answer. RESTful web services utilize the HTTP protocol to serve as the means for communication between the clients and servers.

What are the messages being sent by RESTful Web Services?

Answer. RESTful web services utilize the HTTP protocol to serve as the method for communication between the server and client. The client transmits an HTTP Request in the format in form of HTTP Request.

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When the response is received, the server sends its HTTP Response. This method is known as Messaging. The messages include metadata and message data i.e. details about the message.

Define the Core Components Of A HTTP request?

Ans. Each HTTP request includes five key elements.

The verb refers to HTTP methods like PUT, and GET DELETE.

URI is the abbreviation for Uniform Resource Identifier (URI). It is an identifier for the server’s resource.

HTTP Version that indicates HTTP version, like HTTP v1.1.

Request Header contains metadata (as key-value pairings) to the HTTP request message. Metadata can refer to a client (or browser) type or the format the clients support, the message body format, as well as cache settings.

Request Body identifies the content of the message or its resource representation.

Is Rest Guaranteed?

How can you be sure that Rest is assured?

ans. In order to test REST APIs, I discovered the REST Assured library extremely useful. It was created through JayWay Company and it is a powerful catalyzer that allows automatic testing of REST-based APIs. REST-assured has a number of great features, including similar to DSLXPath-ValidationSpecification Reuseeasy file uploads, and, with these features, we can handle automated API testing with ease.

How do I declare the API information to the Rest Assured Test?

Ans. Using

  • Given()
  • When()
  • Then()

Name the Most Frequently Utilized HTTP Methods that REST Supports?

Ans. There are a handful of HTTP methods that are available in REST and are the most popular.

GET It requests an item at the request-URL. It is not required to include the request body since it could be deleted. Perhaps it could be cached locally or stored on the server.

POST It sends information to the service to process and should usually provide the new or modified resource.

PUT – Upon request of the URL, it changes the resource.

PATCH If we need to perform a partial update, we employ the PATCH method for the update. Only the parameter that we wish to update. We do not have to send the entire payload to update the resource.

DELETE It deletes the requested resource from the request-URL.

Options It indicates the supported methods.

HEAD It provides metadata regarding the URL of the request.

What is the difference between PUT and POST Operations?

Answer. PUT and POST operations are nearly identical. The only difference is the output generated by these operations.

PUT operation is impotent whereas POST operations can yield an entirely different outcome.

The Post Method is employed to make a brand new account/user in the servers.

When should you use PUT and What is the best time to Use Patch?

A. Let’s assume the below user’s details to illustrate:

"id": 1,
"name": "Sam Kwee",
"email": "", // the email changed, yay!
"address": "123 Mockingbird Lane",
"city": "New York",
"state": "NY",
"zip": "10001"

Let’s say that you’d like to make a change and want to eliminate an address field Now
you can set any parameters you wish to set as the result. In this case, you can modify the current
The fields you want to update will have the values you’d like to change and we will not include the address in our new PUT
request payload. Then you will see the following result:

"id": 1,
"name": "Sam Kwee",
"email": "", // the email changed, yay!
"city": "Washington" // the city was changed
"state": "NY",
"zip": "10003" // zip code changed

Then we’ll use the PATCH method whenever we want to alter the “City” field.


The set of results would look as follows:


“id”: 1,

“name”: “Sam Kwee”,

“email”: “”,

“address”: “123 Mockingbird Lane”,

“city”: “Vegas” city changed

“state”: “NY”,

“zip”: “10001”


Note: So basically PUT is overriding or replacing the current entity, while PATCH is altering the
The entity that is currently in existence.

What is URI? Discuss Its Use in the context of REST Based Web Services. What is its format?

Answer. URI stands for Uniform Resource Identifier. URI can be used as the identification of the resource in the REST architecture.

The goal of an URI is to find the resource(s) in the servers that host the website service. A URI is the one that follows this format:

How do you assess the response value compared to Rest Assured And Assertion?


Example: given().

  • parameters(“firstName”, “John”, “lastName”, “Doe”).
  • when().
  • post(“/greetXML”).
  • then().
  • body(“greeting.firstName”, equalTo(“John”)).
  • body(“greeting.lastName”, equalTo(“Doe”));

How do I insert cookies into Testing using the API by using Rest Assured?


given().cookie("username", "John").when().get("/cookie").then().body(equalTo("username"));

How do you insert headers when Testing API? API by using Rest Assured?


given().header("MyHeader", "Something").

How can I Validate Response Headers using Rest Assured?


get("/x").then().assertThat().header("headerName", "headerValue").

How do you handle Basic Authentication using Rest Assured?


given().auth().preemptive().basic("username", "password").when().get("/secured/hello").then().statusCode(200);

What is Payload in RESTFul Website Service?

Ans. The request body of every HTTP message includes data about the request known as the Payload. This section of the message will be important to the person receiving it.

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We could declare that we have sent the payload via the POST method, however, we cannot do this with < GET> as well as < DELETE> methods.

What are the best ways to conduct API testing?

ans. We perform API testing with the help of the postman tool. We receive a URI along with the JSON Payload from the dev
team, and also collect the authentication information (User name and password) from the development team we get the Authentication details from the dev team, then
modifications to the payload, in accordance with our test cases, and then examine the response accordingly. I do test for

API Response Codes

1xx response to information The request was accepted and the process continues

2xx successful The request was received successfully and understood. It was accepted, understood, and accepted

200 OKThe final response is contingent on the method employed. When making the case of a GET request, for example, the
The response will include an entity that is identical to the resource requested.

2001 Created: The request has been satisfied, which has led to the creation of a brand new resource.

200 Accepted It has been accepted for processing however the processing hasn’t been completed.

3xx redirection – additional actions must be taken for the complete request

4xx error on the client: the request is either incorrect syntax or isn’t completed.

400: Bad Request Server is unable or cannot or will not process the request due to a possible client error
(e.g. (e.g., malformed request syntax, too large, incorrect request message framing, or deceitful
Request routing).

Unauthorized 401: Like 403 forbidden but specifically designed for use in authentication is required.
is required, but has not yet been provided or has not been not yet.

403 To be blocked: The request contained valid data and was accepted by the server however the server was not able to process it.
Refusing to take an action. It could be because that user’s not possessing the required permissions to access the resource.

404 Not FoundThe requested resource couldn’t be found, however, it may be made available in the near future.

5xx error on the server – the server was unable to process an apparently legitimate request.

500 Error on Internal Server
The generic message of error that is displayed when an unexpected situation was observed, but not more
The specific message you are looking for is appropriate.

The 501 is not implemented
The server does not recognize the method of request or is not equipped with the capacity to meet the request.
Usually, this implies that the API will be available in the future (e.g. an upcoming feature in Web-service API).

502 Bad Gateway
This server was acting as a proxy or gateway and received an untrue answer from its upstream

503 Service Not Available
The server is not able to process this request (because it is overwhelmed or is down to maintain).
In general, it is an unavoidable condition.

504 Gateway Timeout
It was serving as a gateway, and proxy and didn’t receive a prompt response from the
Upstream server.

What API details are available to users of Web Developer tools?

Anas. Request headers, Response body Cookies for Response.

What kind of encryption does postman use to accept authorization credentials?

The answer. Postman accepts Base64 encoded data only. Because it converts the information into textual form and
It is sent in a simpler format like HTML data from forms.

Are our global scope variables able to have names that are duplicated in Postman?

Analyze. Since global variables are global i.e. without any specific environment globally, global variables can’t be duplicated.
names. Local variables could be named the same they may be in different settings.

What is a Postman Collection?

ans. A Postman Collection allows us to group requests together. It allows us to arrange the
Requests are placed in folders.

What is the meaning behind the monitors of the postman?

ans. The postman monitor is used to run collections. Collections run until a specific duration as defined by
The user. Postman Monitor requires the user to sign in. Monitor reports are shared with users
by email on a monthly/daily basis.

What are you able to understand by the word Postman Collection runners?

Answer. A postman collection runner is utilized to conduct data-driven testing. The set of API requests
The data is collected in a collection to allow to run off multiple iterations using various sets of data.

How can you eliminate local variables?

Answer. Local variables are immediately deleted after tests have been run.

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What can we do to stop the execution of requests, or stop the collection process?

Ans. postman.setNextRequest(null);

How do we get access to the Postman variable?

ans. We can access the Postman variable by typing the |}

How can you run 100 times a request in Postman?

Ans. By using Collection Runner

What are the first steps to take in the Collection Run?

Ans. Pre-request scripts on level Collection level are first executed during the Collection run.

How do we track the requests and replies in Postman?

Ans. You can access the logs of requests and responses via Postman Console. Postman Console screen.

What are the biggest difficulties of API testing?

Ans. The most challenging aspect of API testing is

  • Parameter Selection
  • Parameter Combination
  • Call sequence

What kinds of Bugs that API testing find?

Ans. The different types of Bugs, API will find

  • Incomplete or redundant functionality (Functionality Bugs): Before analyzing how the API works, the tests should verify if the API functions function correctly or not. It starts by checking the basics of functions like the ability to create and delete data using API calls when appropriate. The tests also check for functionality issues that have not been addressed, such as when the API requires features that aren’t available.
  • Stress

Does API Testing Function In Consistency?

Ans. If we can are able to get the API to work, it’s an excellent first step, but the API must be working every time. Testing APIs helps to identify problems in the event that integrations are present between various modules.

Does API Testing Help Protect Data Exchanges?

Ans. Then, API testing finds security-related issues. API calls transfer data between the endpoints. If they are not protected, then hackers could use them to their advantage. Even if the data is private. The API test checks if the data sent via HTTP is encrypted correctly.

  • Flags that have not been used
  • Errors that are not implemented
  • Inconsistent error handling
  • Performance
  • Multi-threading problems
  • Improper errors

Define the API testing method?

Ans. Mentioned below are the main factors that influence the methodology:

  • Create test cases that are appropriate to test the APIs and employ testing techniques such as boundary value analysis Equivalence class, etc. to verify the capabilities.
  • Examine the functions that result from the combination of more than two parameters with value.
  • Define the scope and capabilities of the API program. API program.
  • Determine the precise input parameters.
  • Execution of the test case and comparison of outcomes with the expected results.
  • Analyzing API behavior under certain conditions such as the connection to files, and so on.

What is the difference between HTTP and HTTP?

Ans. HTTP is the abbreviation for Hypertext Transfer Protocol and it’s a protocol and syntax used to display information for the transfer of data over networks. The majority of information sent through the Internet such as website content and API calls utilizes an HTTP protocol.

It is important to note that the S in HTTPS signifies “secure.” HTTPS uses TLS (or SSL) to secure HTTP requests and their responses, as in the above example instead of seeing the words, an attacker will be able to see a variety of random characters.

“If an online site uses HTTP rather than HTTPS it is possible for all requests and responses could be read by anyone monitoring the session. In essence, a malicious person could read the content in the request as well as the response and determine exactly the information is being requested by the user and/or sending and receiving.”

The difference in API as well as Web Services?

Ans. Web services are any type of service which are available on the Internet and then normalizes the correspondence via XML encoders.

API is an abbreviation for Application Programming Interface. It’s a collection of subroutines and communication conventions. Developers are able to use various API tools to make their programs easier and less complicated. “All APIs for web services are APIs but not all APIs are Web Services.”

What is the difference between authorization and authentication could be?

Authentication vs. authorization

Ans. Authorization and authentication might seem similar, however, they’re more closely related to identity and
Access administration (IAM).

Authentication ensures that users are who they claim to be. are. It is a way of ensuring that Authentication verifies the identity of the person who is authenticated and authorizes authorization to the identified users to access resources.

In simple terms, Authentication is “Who do you think you’re” It’s about proving your identity. The word “authorization” means “What you are able to accomplish” This is all related to accessing. It is about does you have the right to have access to something.