Top 40 API Testing Interview Questions and Answers Prepare Now
Tejasvee Sharma
Feb 15, 2022
Whenever you are looking for a job, you’d want to get a clear picture of what exactly the employer expects out of you. To be able to do that, you’d probably have to look at the interview questions the employer asks. There are numerous API Testing interview questions and answers floating around, but it is not easy to find the right ones. We have mustered some really useful API Testing interview questions and their answers which provide you with a 360° view of the interview process and put things in perspective. With this, you are sure not to experience any surprises when you walk into an interview.
About API Testing: API testing is the process of verifying that an API works as expected. The tests can be performed using Postman, Mountebank, and curl commands or other software depending on which language the API is written in. API testing is important because it ensures that the API works as expected and meets the requirements of the end-users. It can also help to identify any potential issues with the API before they become major problems. API testing is typically performed by a QA engineer or a developer who is familiar with the API. It can be a valuable tool for both small and large companies.
API testing is a type of software testing that involves testing APIs (Application Programming Interfaces) for quality and correctness. API testing can be used to evaluate the functionality of an API, identify any issues, and determine whether the API is meeting the expectations of the developers and users. API testing can also be used to verify the security of an API.
API testing is a specialized type of testing that requires a good understanding of both the API and the systems that are dependent upon it during each phase in order to ensure maximum reliability while maintaining productivity levels on your projects – this includes requirements gathering, developing test cases/tests using SDK or other third-party tools & verifying findings, etc. The goal here is not to replace GUI testing rather augment it.
API testing has emerged as a critical tool for quality assurance in the software development process. By performing API testing, developers can ensure that the APIs they create meet the expectations of their users and other stakeholders. API testing can also help developers identify and fix bugs and issues with their APIs.
3. Tell some common tests performed on API’s
The API should verify if the API is updating any data structure.
Verify if there is a return value.
Based on the input conditions, the results returned from the API are checked.
Verification of the API to check if it causes any other action or calls another API
4. What's the difference between UI level testing and API testing?
UI level testing refers to graphical interface testing as a type of software testing that involves checking the graphical interfaces of applications and their elements like fonts, images, layouts, etc. UI testing focuses on the appearance of a software application.
An API is a set of protocols and conventions for communication between two software systems, and it allows their integration. In a programming language, a software system implementing an API includes certain functions or subroutines that are meant to be invoked by other programs or software system.
5. What is SOAP?
SOAP (Simple Object Access Protocol) is an XML-based protocol designed to allow programs to communicate and exchange information with one another.
6. Define REST API?
It’s a set of functions to which a programmer performs requests and gets responses. In the REST API, interaction happens via HTTP protocol.
REST means Representational State Transfer and is fastly becoming the de facto measure for API creation.
7. How do you test APIs?
In order to test your API, follow these steps.
Select the suite that you want to add your test case into
Select test development mode
Develop test cases for all your APIs
Configure application control parameters
Configure test conditions
Configure method validation
Execute API test
View test reports
Filter API test cases
Sequence API test cases
8. Mention the primary areas considered while writing API documents?
When creating API documentation, the main focus should be on
Source of the content
Document plan or sketch
Delivery layout
Information needed for each function in the document
Automatic document creation programs
9. What you think is considered when writing API document?
Source of the content
Delivery layout
Document plan or sketch
Automatic document creation programs
Information is required for every function in the document
10. Name the popular API documentation tools?
The most popular API documentation tool is JavaDoc (for Java code) Doxygen (for .Net code), which is used in the development of API documentation.
11. Explain API framework?
The API is self-explanatory. The config file is used to maintain a listing of your device’s configuration settings. It is required that automated test cases be formatted in parse-table. When testing the API, it’s not necessary to test every API Because all of its APIs are active for a specific run, the config file contains some section whose all APIs are inactive by default.
12. Tell me the way the API Builder work?
The API Builder is a PL/SQL program made up of four SQL files
Once the API’s parameters are set and the process is started, a single file is in charge
There are two files that are created for temporary tables and a Master package to create the outputted code.
The final file, output_script.sql, is produced by the SQL process and created on disk.
13. What is TestApi?
TestApi is a collection of utility and test APIs, providing frameworks to develop testing tools and automated tests for web applications .NET and Win32 application. It contains a set of building blocks, types, data structures, and algorithms.
14. Explain Input injection and different ways of doing it ?
Input Injection: It is a form of simulating user input, in many different ways.
Simulation using a device driver
Direct Method Invocation
Simulation using a robot
Invocation using an accessibility interface
Simulation using low-level input
15. What are the challenges of API testing?
The challenges in API testing are
Parameter Selection
Parameter Combination
Call sequencing
16. What does Runscope mean in API testing?
Runscope is an amazing web tool that helps developers test their APIs with ease using backend services and interface.
17. What are the basic rules of API test design?
Setup: Start and stop services and create new objects.
Execution: Steps to develop API or Scenario, also log
Verification: Oracles to evaluate execution outcome
Reporting: Pass, failed, or blocked
Clean up: Pre-test state
18. Name the types of Bugs, API testing will find?
The types of Bugs, API will find
Improper errors
Missing or duplicate functionality
Stress
Fails to handle error conditions gracefully
Reliability
Unused flags
Security
Not implemented errors
Performance
Inconsistent error handling
Multi-threading issues
19. What tools are used for API test automation?
While testing Unit and API testing you need to have the similar target source code. If an API is testing a code based on .NET then the tool which is supporting should have .NET. Tools that can be used are:
NUnit for .NET
JUnit for Java
HP UFT
Soap UI
20. How to describe every API function in the API documentation?
Description: Small description of what a function does
Syntax: Syntax around parameters, order of arguments, required elements, and any optional.
Parameters: Function parameters
Error Messages: Error message syntax
Example Code: Tiny piece of code
Related Links: Related functions
21. Tell us the steps for testing API?
Pick the test case to be performed
For API calls create a test case
To meet the test case configure the API parameters
Govern how will you authenticate a successful test
Using programming languages like PHP or .NET perform the API call
Permit the API call to return the data to validate
22. Name some protocols that are testing in API testing?
HTTP
SOAP
JMS
REST
UDDI
23. Name the types of API testing?
Unit Testing
Load Testing
Functional Testing
Runtime/Error Detection
UI Testing
Security Testing
Interoperability and WS compliance Testing
Fuzz Testing
Penetration TestingA
24. Explain API test environment?
The need to test an API often requires a complex approach. In order for the server configuration and the database, as well as all the dependencies to be in accordance with the software application requirements. After the installation, API is checked to see if it works properly. API testing doesn’t use any graphical user interface.
25. Explain API framework?
The application programming interface (API) for ASP.NET contains a file named config.xml, which lists all the web API’s that must be initialized and also listed for the particular site. Every test run doesn’t need all APIs.
26. Tell the limits of API usage?
Many API providers have certain limits on APIs working. So you should try to estimate your usage and know how much it will affect the cost of the service.
27. What needs to verify in API testing?
Accuracy of the data.
Response time.
HTTP status code.
Error codes in case API return any errors.
Authorization.
Non-Functional testing like performance testing, security testing.
28. Name some popular templates for API documentation?
Here are some popular templates that make the complete process simple and easy:
Swagger
Slate
Miredot
FlatDoc
RestDoc
API blueprint
Web service API specification
29. Explain Resource in REST?
The REST architecture treats every content as a resource, it doesn’t matter whether the content is text files, HTML pages, images, videos, or a database. A REST server will give the functionality to access resources and modify them. Each resource can be identified by a unique URIs/ global IDs.
30. What is the right way of representing a resource in RESTful Web
REST uses different representations to define the resources. The most popular representations a resource are XML and JSON.
31. Name the protocol used by the RESTFUL Web Services?
It uses the HTTP protocol. The HTTP protocol is used to communicate between the client and server.
32. Explain the characteristics of REST?
REST isn’t a stateful protocol, so every time you call the REST service, it starts up a new instance and replaces any data that was previously stored in memory. To make sure it doesn’t make too many requests, REST implementations often limit the number of times a request can be repeated in a given timeframe.
Web Services use the POST method to execute operations, while REST uses the GET method to access the resources.
33. Explain messaging in RESTFUL Web Services?
HTTP is the communication protocol used by web servers for sending information to the web browser. The messaging feature allows for the client to send a message in the form of an HTTP request, which is then responded to by the server in the form of an HTTP response. This message consists of two parts - the actual message data, and metadata that describes the message.
34. Explain the components of an HTTP request?
An HTTP request has five elements. These are:
Action showing HTTP methods: like GET, POST, PUT, and DELETE.
Uniform Resource Identifier (URI): The URI of a resource is the identifier for the resource on the server.
HTTP version: Specify the HTTP version like- HTTP V1.1.
Request Header: The request header can carry metadata for the HTTP request message. Metadata may include things like the client software, the body format, and the client cache settings.
Request Body: A resource body is a message’s content or its representation.
35. Can we use GET request rather than PUT to create a resource?
PUT or POST method is used develop a resource whereas GET is used to request the resources.
36. Explain URI and its purpose as a web-based service?
URI (Uniform Resource Identifier) is a naming scheme that is used to identify Internet resources such as files or web pages. A URI can be used to identify an object on the internet. The purpose of URI is to find the resource which should be hosted by the web service.
A URIs format is :////
37. When we can use SOAP API?
The SOAP API provides all functionalities required to perform operations on records, such as creating, retrieving, updating, and deleting them. It can be used to manage passwords, perform searches and perform other
38. Name commonly used architectural styles for creating a Web API?
There are four common Web API architectural styles:
Simple URI as the address for the services
HTTP for client-server communication
Stateless communication
XML/JSON as a formatting language
39. What kind of tools can be used for API testing?
There are numerous programming API testing tools readily available for testing APIs. A few of the popular ones are Postman, SoapUi Pro, Apigee, etc. When it comes to unit and API testing, a target can be seen as source code. If an API method calls a .NET method, a supporting tool must be .NET.
40. Name the testing methods that come under API testing?
Load testing to test the performance under load
Unit testing and Functional testing
Discovery testing to list, build and delete the number of calls documented in API
API documentation testing to determine its efficiency and effectiveness
Security and Penetration testing to validate all types of authentication
Usability and Reliability testing to get consistent results
End to end Integration and Web UI testing
Automation testing to create and run scripts that require regular API calls
41. State the reasons why is API testing taken as the most suitable form for Automation testing?
The automated testing tool performs all functional paths of the tested software very well.
It gives the most stable interface.
It saves you a lot of time. It provides fast feedback.
