API Testing Practice Test 2026: Free QA Exam Prep

API Testing Automation 2026

API testing is a kind of software testing that examines APIs' functionality, dependability, performance, and security. It is also one of the most important aspects of software testing and often requires a different skill set and testing tools than other types of software tests. API testing includes the testing of an application programming interface (API). An API is a set of functions, procedures, and classes that software or hardware provides to support requests from applications or programs. A programmer can use the API to access different parts of his application or to facilitate communication between programs in a controlled way.

Programmers can also use it to create new code that works with a specific operating system, hardware, and other programs. Applications integrated with APIs can be distributed more easily across various platforms. Programmers typically use several different API tools to manage the amount of work for a large project. API tools can work together with a programming language if the API is well defined.

XML API for Testing

The Cloud Storage XML API programmatically provides a RESTful interface for managing Cloud Storage data. XML supports more operations than the JSON API does. XML API for testing allows a quick and easy way to test your application by accessing all of your content in Cloud Storage easily and quickly when you are on the go or at work or want to avoid writing some complex code.

This Cloud Storage XML API is only available as part of the Google Cloud Platform Console. It's ideal for tasks that require processing large amounts of data. It's designed to be used in a variety of applications, including backend services to support mobile or web applications, workflow processing systems that need to process input files along with their associated metadata in an automated way, or media asset management systems where users aggregate information from multiple sources into an accessible database format.

💡 API Testing Basics

What is API Testing?: API Testing validates the behavior, reliability, performance, and security of application programming interfaces to ensure they return correct responses and handle requests properly.
Why is API Testing important in modern applications?: API Testing is critical because most modern systems are service-based, and failures at the API layer can break integrations, microservices, and user-facing workflows even when the UI looks stable.
What skills are measured in an API Testing certification exam?: The API Testing exam typically measures your understanding of HTTP, REST, authentication, test design, automation tools, and how to analyze responses, logs, and defects in API-driven systems.
Who should take the API Testing exam?: The API Testing exam is ideal for QA engineers, SDETs, developers, and test leads who work with backend services and want to prove their skills in automated and manual API Testing.

📋 API Testing Format

How is the API Testing exam structured?: The API Testing exam is usually divided into objective questions, scenario-based items, and sometimes practical tasks that simulate running or analyzing API tests.
How many questions are on a typical API Testing exam?: Many API Testing exams include around 50–80 multiple-choice or multiple-select questions, though the exact number depends on the specific certification body.
How long do you have to complete the API Testing exam?: You typically have 90–150 minutes to complete the API Testing exam, giving you time to read scenarios carefully and apply your test design knowledge.
What types of questions appear on the API Testing exam?: The exam often mixes definition questions, real-world scenarios, code snippets, and tool-based questions that test how you design, execute, and interpret API tests.

📝 API Testing Registration

What are the eligibility requirements for the API Testing exam?: Eligibility usually requires basic software testing knowledge, familiarity with HTTP and REST, and sometimes prior QA experience or a related certification.
How do I register for an API Testing certification exam?: You register by creating an account with the certification provider, selecting the API Testing exam, choosing a date and delivery format, and paying the exam fee.
What identification do I need on API Testing exam day?: Most providers require a valid government-issued photo ID that matches your registration name, and some may ask for an additional secondary ID.
How much does it cost to take an API Testing certification exam?: API Testing exam fees vary by provider but often range from modest entry-level prices to higher fees for advanced certifications, with separate costs for retakes.

✅ API Testing Passing & Results

What score do I need to pass the API Testing exam?: Passing scores are typically around 65–75%, though each vendor sets its own cut-off and may use scaled scoring.
How is the API Testing exam scored?: The exam usually awards points for correct answers, may weight some scenario questions more heavily, and then converts your raw score into a scaled score or percentage.
How long does it take to receive my API Testing exam results?: Some API Testing exams show provisional results immediately, while official score reports or certificates may take a few business days to be released.
Can I retake the API Testing exam if I fail?: Yes, most programs allow retakes after a waiting period, but each attempt usually requires another registration and payment of the exam fee.

📚 API Testing Preparation

How should I prepare for the API Testing exam?: Combine a structured study guide, hands-on practice with real APIs, and timed practice questions to build both conceptual understanding and exam stamina.
Which API Testing topics should I focus on most?: Focus on HTTP methods, status codes, REST design, authentication, validation of JSON or XML, negative testing, and automation frameworks commonly used in API Testing.
Are there official practice tests or mock exams for API Testing?: Many certification providers and training platforms offer practice questions or full mock exams that mimic the style and difficulty of the real API Testing exam.
How far in advance should I start studying for the API Testing exam?: Most candidates begin studying four to six weeks before the exam, allowing enough time to review theory, practice with tools, and close knowledge gaps.

Error Codes in API Testing

Error codes in API testing are a pain to deal with. They're not always obvious and can appear during any phase of the testing process — during testing, staging, or production. Here are the common API testing error codes: For more preparation, try our ISTQB practice test. For more preparation, try our AWS practice test.

Error Code	Description
badRequest	The API request is incorrectly constructed or invalid. As a result, the API server was unable to comprehend the request.
notModified	The If-None-Match header's condition was not satisfied. This answer indicates that the requested document has not been changed and that a cached response should be obtained. Examine the If-None-Match HTTP request header value.
unknownApi	The API that the request is attempting to access is not recognized.
temporaryRedirect	Resend your request to the URL given in the Location header of this response to have it processed.
notFound	The requested operation failed because the required resource could not be located.

What are the challenges faced in API testing?

When evaluating API implementations, software testers encounter several distinct challenges. Here are the common challenges in API testing:

Parameter Combination - APIs manage system communication by assigning data values to parameters and transferring those parameters via data requests. All potential parameter request combinations must be tested in the API to test for faults.
Parameter Selection - API calls result in varying levels of information and functionality. The system response itself may be available in the API documentation, but the number of parameters required to make the call differs. Additional parameters may be necessary to create a more robust response.
Call Sequencing - API calls may be sequenced in any order, meaning earlier API calls must complete successfully before subsequent API calls can be made. This presents additional test challenges when working with multiple APIs. Errors may occur due to timing issues, logic errors, or difficulty debugging the call sequence.

API Testing Questions and Answers

What is API testing?

API testing is a type of software testing that validates application programming interfaces (APIs) directly, rather than testing through the user interface. It checks functionality, reliability, performance, and security of APIs — including REST and SOAP services — and is a core skill for QA engineers.

What are the most common HTTP methods tested in API testing exams?

The five most-tested HTTP methods are GET (retrieve data), POST (create a resource), PUT (replace a resource), PATCH (partial update), and DELETE (remove a resource). Exam questions often ask you to identify the correct method for a given scenario.

What HTTP status codes should I know for an API testing exam?

Key status codes include: 200 OK, 201 Created, 204 No Content, 400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found, 405 Method Not Allowed, 409 Conflict, 422 Unprocessable Entity, 429 Too Many Requests, 500 Internal Server Error, and 503 Service Unavailable.

What tools are commonly used in API testing?

Postman is the most widely used GUI tool for manual API testing, while REST-assured (Java) and requests (Python) are popular for automation. Other common tools include SoapUI (SOAP/REST), Insomnia, Newman (Postman CLI), Karate, and k6 for performance/load testing of APIs.

What is the difference between REST and SOAP APIs?

REST (Representational State Transfer) is an architectural style that uses standard HTTP methods and typically exchanges JSON data. SOAP (Simple Object Access Protocol) is a protocol that uses XML messages and supports built-in security (WS-Security) and ACID transactions. REST is lighter-weight and more common in modern web services; SOAP is preferred in enterprise and financial systems.

What authentication methods are tested in API testing exams?

Common authentication types include API Keys (sent in headers or query strings), Basic Auth (Base64-encoded credentials), Bearer Token / JWT (JSON Web Token), OAuth 2.0 (authorization framework), and HMAC signature-based auth. Exam questions often ask you to identify the correct auth header format or the security risks of each approach.