API testing evaluates an API's performance, reliability, and functionality through automated checks. Common errors include 400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found, 429 Too Many Requests, and 5xx server errors. Popular tools include Postman, SoapUI, Swagger, Insomnia, and Jmeter. Read more on this topic at StudySection Blogs.

1. What is API Testing? A Brief Introduction
An API comprises programming codes designed to streamline data transmission between
software products, specifying the terms of this interaction.
An API is like a messenger that helps different software talk to each other by following specific
rules. It's not like a user interface where you directly interact with an application. Instead, it
works behind the scenes, letting one software ask for data from another and get a response. It's a
middleman that helps software exchange information smoothly.
API Testing Tools
● API testing tools are the software programs used to analyze an API's performance,
reliability, and functionality.
● It automates sending requests to the API and checking the responses.
● These tools look for errors and discrepancies in the API behavior.
● Features of an API testing tool include test case creation, request and response validation,
data-driven testing, and reporting.
● Some of the most popular API testing tools are: Postman SoapUI Swagger Insomnia
Jmeter
Common API Errors:
To debug API errors effectively, understanding HTTP status codes is crucial. Here's a breakdown
of common status codes and how to handle them:
● 400 Bad Request: This indicates an issue with the request itself, often due to syntax
errors or missing parameters. Ensure all request components are correct, including
endpoints, headers, and JSON bodies. Validate input using tools like JSON Lint.
● 401 Unauthorized: This occurs when authentication credentials are missing or invalid.
Double-check the format of the authorization header, ensuring tokens are properly
formatted (e.g., "Bearer token") or credentials are base64 encoded for basic
authentication.
● 403 Forbidden: Unlike 401, this indicates valid authentication but insufficient
permissions. Verify that the user has the necessary access rights, such as requesting
appropriate API access tokens or ensuring correct user roles.
● 404 Not Found: It means the endpoint doesn't exist, the resource isn't found, or the user
lacks permissions. Review API documentation for endpoint existence and spelling
accuracy. Ensure the user has access to the resource.
● 429 Too Many Requests: Indicates exceeding rate limits, common in public APIs.
Check for a Retry-After header for retry timing. Review API documentation for
rate-limiting specifics or contact support to adjust limits.

2. ● 5xx Error Codes (e.g., 500, 502, 503, 504) indicate server-side issues. Wait and retry
later, as the server may be under heavy load or undergoing maintenance. Check the API
status page for updates or maintenance notifications.
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