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Congratulations! That long-awaited email is here. An email regarding your job interview for an API tester.
So, you are here looking for the most common API testing interview questions. You are doing the right thing. It is always recommended to prepare for these frequently asked questions before an interview. And we understand the importance of it.
API (Application Programming Interface) testing is considered the future of software testing because of its endless advantages, time effectiveness, language independence, or GUI (Graphical User Interface) integration, etc. Today, API testing has become a must-have requirement for all software testing projects to ensure maximum product quality. This can be done by the Automation Testing Certification Program which will guide you through different levels of testing and make you understand the concepts of QA testing. This course will brush up your skill and make you prepare for your API testing job.
Whether you are a fresher or experienced, we have prepared these most frequently asked API testing interview questions taking reference from actual interviews to help you ace your next interview.
Here are the basic interview questions on API testing that you must start with.
Q1. What is an API?
Ans:- This is the most basic and crucial question among the API testing interview questions
API (Application Programming Interface) is a software intermediary that helps communication and data exchange between two software systems.
You can also give more information about the API examples such as Google Maps API, Youtube API, Twitter API, AmazonAdvertising API, and if you have previously worked on any.
Q2. What is API Testing?
This question is mostly asked question among the API interview questions to check if you can efficiently frame your answer.
Ans: API testing is the testing of the developed APIs to check their functionality, efficiency, reliability, and security.
You can mention types of API testing such as
Q3. What are the advantages of API Testing?
Give this answer in a way to show the interviewer the importance and relevance of API testing and where and how you are going to use it or have already used it.
Q4. How does API work?
Ans:- Generally, API takes a request, and processes it which is data validation, database interaction, and data processing, and then the result is reverted to the source. A complete guide on API testing can be found in our API testing tutorial for beginners which gives an in-depth analysis of API testing and its vital concepts.
Q5. Do you know about the common tests performed on the APIs?
Ans:-Here is the list of common tests that are performed on APIs –
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Q6. What are the protocols used in API Testing?
Ans:-These are the protocols used in API testing:
Q7. What are the most commonly used tools in API Testing?
Ans:- Among the long list of software testing tools, some of the API testing tools available are Postman, Katalon studio, SoapUi, Apigee, JMeter, Parasoft SOAtest, Apigee, API fortress, JUnit, etc.
Q8. What to perform API test?
Q9. What should you take care of while writing cases?
Ans:-These are the points you can reply with
Q10. What needs to be verified in API testing?
Ans:-In API Testing, we usually send a request to the API, and then we analyze the responses keeping the following parameters in mind:
Q11. Define Test Data.
Ans:- Test data is the input data used to perform test cases. This data can be prepared either manually or by using different tools. For example, to test the login functionality of an application, the input data will be username and password which constitutes the test data.
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Q12. Define test coverage.
Ans:- Test coverage amount of testing performed by making use of test cases. It can be either functional testing or non-functional testing.
Q13. What is a SOAP web service?
Ans:- SOAP means Simple Object Access Control Protocol and this is an XML-based protocol that is used to exchange information between computer machines.
Q14. What do you understand about the REST API?
Ans:- Rest ( REpresentational State Transfer) API is defined as the set of functions that helps a developer in sending requests and receiving responses. In this protocol, the interaction is always made through an HTTP protocol. The meaning of REST is Representable State Transfer that has become a defacto standard for API creation these days.
Q15. How will you differentiate the API testing and the UI testing from each other?
Ans:- UI or User-Interface testing is used to check the graphical interface of an application or software program, how the user interacts and reacts to different elements like fonts, images, layouts, etc. This testing is majorly focused on the look and feel of an application.
At the same time, API enables communication among two different software components. Any software system implementing an API contains functions or subroutines that can be executed by any other software system.
Q16. How will you differentiate between API Testing and Unit Testing?
Performed by QA team
Performed by the development team
This is a form of black-box testing
This is a form of White box testing
Full functionality of the software is checked as it will be used by external developers (The end-user)
Here each unit is tested for functionality.If each unit is performing well in isolation.
The tester usually does not have the access to the source code, only the functionality test is done.
The developer has the access to the unit test cases as they test these before they proceed for the next step.
Q17. What is test documentation?
Ans:-The API documentation is technical writing giving instructions on how to use and integrate with an API efficiently. It gives reference to the information needed to work with the API and helps you get API testing questions.
Q18. When you are writing an API document, what are the major areas to focus on?
Ans:-Here is the list of major areas that you should focus on while writing an API document –
Q19. For any API document, how can we document different functions?
Ans:-Syntax – Here, you have to write the syntax for the parameter of the code in the same sequence as they occur, highlight necessary elements, optional elements, etc.
Q20. Mention the list of tools that are needed for the documentation.
Ans:- There are a number of API testing tools required for the documentation. Among them, SOAP UI, Katalon Studio, Postman, Apigee and Tricentis Tosca are some of them to suit every business requirement.
For Java Code, you can use JavaDoc and for the .Net code, you can use Doxygen.
Q21. Difference between API and Web services?
All APIs are not web services
All web services are APIs
All APIs need not be exposed over the web(i.e. HTTP)
All web services need to be exposed over the web(HTTP)
API uses multiple ways for communication e.g. DLL files in C/C++, Jar files/ RMI in java, Interrupts in Linux kernel API, etc
A Web service uses only three styles of use: REST, SOAP, and XML-RPC for communication
A Web services are network dependent
APIs don’t need a network for operation
As you are now aware of the API interview questions asked for freshers, Now let’s move towards the advanced API interview questions, also check out the key role and responsibilities of an automation tester. Get prepared for all the API interview questions, You never know!
Here are the API interview questions that you should prepare while appearing for the senior profiles. These API testing interview questions are mostly asked to test your knowledge and experience, so try to impress your interviewer by exposing your skill and knowledge.
Q22. What is the basic process to test an API? Explain based on your previous experiences.
Ans:- Here are the basic steps to follow to test an API –
By following these steps in the same sequence as given, this is easy to test an API successfully.
Q23. What are the errors expected during API Testing?
Ans:-These are the errors you can tell to let them know that you have performed such tests before and you know what you claim.
Q24. What are the major challenges faced while performing API Testing?
Ans:- This is one of the most asked API testing interview questions.
You can always talk about the challenges you perform while doing API testing, or the list can go like this.
Q25. What is the test environment of API?
Ans:- Setting up an API environment is not easy, so try to share your experience and try to communicate with the interviewer on this.
The test environment of API is a bit complete and requires the configuration of both database and server is done without the integration of GUI.
After installation, API is verified for the right operation. Throughout the process, we study the test process by setting up the API with different parameters.
Q26. What are the principles of an API test design?
Ans:- It is one of the API design interview questions. You can answer it like this:
The seven principles of API test design are listed below.
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Q27. What do you understand by Black Box Testing?
Ans:- Black Box Testing is a method of software testing where the testers evaluate the functionality of the application without peering into the internal source code. This method can be applied in every level of software testing such as integration testing, unit testing, system testing, and acceptance testing.
Q28. What do you understand about the API Framework?
Ans:- There is no need to give an introduction to the API Framework as it is self-explanatory. When you are testing APIs then you don’t have to work on each API independently but you can use config files in that case where details for all APIs are given and can be used if needed.
Q29. Explain the working of API builders.
Ans:- API builder is a PL SQL program that is made up of four SQL files where one file is responsible for starting the process, two files are used to create the temp tables or the master package, and the fourth file will help in generating the final output.
Q30. What is a Test API?
Ans:- Test API is a set of test APIs or a library of utility that helps developers or testers in creating testing tools and automated test cases for .Net or WIN 32 applications. It also offers a set of basic building blocks, data structures, data types, algorithms, etc.
Q31. How do you test the API security?
Ans:- For testing the security of API during API testing, we need to validate 2 things:
We can also check whether the TLS or the SSL certificate used over the HTTPS protocol is valid or not.
Q32. What are the different types of Input Injection and what are the different ways of stimulating user input?
Ans:- Input injection is a popular act of simulating user inputs and it can be done in popular ways as listed below –
Q33. How to perform the API testing with Run Scope?
Ans:- Run Scope is a web application that supports backend services and easy to understanding user interface tool for testing APIs.
Q34. What are the different principles of API testing design?
Ans:- Test design includes processes for identifying test cases. The major principles include – Setup, Execution, Verification, Reporting, Clean up, etc. You can read our blog on test case design techniques for a better understanding of test design.
Q35. What are the tools that should be used for API test automation?
Ans:- The automation tools that are frequently used for API test automation include – JUnit for Java, SOAP UI, HP UFT, or NUnit for .NET, etc.
Q36. What is caching and how does it work?
Ans:- Caching is a mechanism to improve the performance of applications. It is a process of storing and accessing data from a cache. A cache can be defined as a software or hardware component intended at storing data so that future requests for the same data can be retrieved faster.
e XML, like the SMTP server or POP3 protocol to pass the messages or reply to queries.
Q37. Name some commonly used API documentation templates?
Ans:- There are numerous API documentation templates available to make the entire process simple and straightforward.
Get a complete PDF of API Testing interview questions here!
These are 7 rest assured API automation testing interview questions and answers to give you a knowledge of REST assured, RESTful web services, URI, and the types of HTTP methods. You can face such API questions too.
Q38. What is REST assured?
Ans:- REST Assured is a Java-based library that is used for RESTful APIs testing. It can be used to test applications based on JSON and XML. Also, all methods are entirely supported, including PUT, POST, GET, PATCH, and DELETE.
Q39. What are RESTful web services?
Ans:- Restful web services are REST Architecture-based Web services. RESTful web services use HTTP as a communication between the server and the client.
Q40. What is URI?
Ans:- URI (Uniform Resource Identifier) consists of the base URL, path parameter, and query parameter.
Q41. Which HTTP methods are used in REST and what do they do?
Ans:- You definitely should remember these HTTP methods before going to appear API testing interview questions.
Q42. Can You explain the payload?
Ans. Payload/body is highly secured input data that is sent to API to process the request. The payload is usually in JSON format in REST API.
Q43. What is the difference between PUT and POST?
Ans. The main difference between PUT and POST is PUT requests are idempotent. Calling the same PUT request multiple times will always respond with the same result. In contrast, calling a POST request repeatedly have the side effects of creating the same resource multiple times.
Q44. can we use GET request instead of PUT to create a resource?
Ans. The PUT and POST method is used to create a resource. GET is only used to request the resources.
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Q45. What are SOAP Web services?
Ans:- This is one of the fundamental API testing interview questions that you must know the answer to.
The SOAP (Simple Object Access Protocol) is defined as an XML-based method used in web services. It is both platform and language independent.
It is well known for designing and developing web services. It also enables the communication between applications developed on different platforms using various programming languages over the Internet.
Q46. How does SOAP work?
Ans:- SOAP provides a user interface that can be accessed by the client’s server object, and the request sent by it goes to the server, which can be accessed using the server object. The user interface creates some files or methods consisting of server objects and the name of the interface to the server object.
It also contains other information such as the name of the interface and methods. It uses HTTP to send the XML to the server using the POST method, which analyzes the method and sends the result to the client.
The server creates more XML consisting of responses to the request of the user interface using HTTP. The client can use any approach to send the XML, like the SMTP server or POP3 protocol to pass the messages or reply to queries.
Q47. What are the syntax rules for a SOAP message?
Ans:- These are some basic syntax rules for an SAOP message
Q48. How do users utilize the facilities provided by SOAP?
Q49. Tell the elements of SOAP message structure
Ans:- It is an ordinary XML document that contains the elements as a SOAP message
Q50. What are the obstacles users face while using SOAP?
Ans:- The major difficulty faced by users using SOAP is a firewall security mechanism. This locks all the ports leaving some like HTTP port 80 used by SOAP that bypasses the firewall.
The major technical issue with SAOP is, it mixes specifications of message transport and message structure.
The above-mentioned advanced API testing interview questions and answers will be very helpful for you when an interviewer will focus on finding out the functional knowledge of the domain.
These API testing interview questions have been extracted from real-time interviews, and are found to be mostly asked. So, better prepare them with sheer dedication, attention, and confidence.
For cracking these API testing interview questions, you should have practical knowledge when working with any technology and to help you get that, enroll in our automation testing training online.
If you have any queries on these interview questions on API testing, feel free to contact us via commenting down below or hitting our free career counseling!
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