Uncovering API Testing Bugs: Common Types and Effective Remedies

Blog API Testing
Rishabh Patel
06 Sep, 2023

In the dynamic world of software development, APIs are the linchpin for connecting applications and services seamlessly. This blog is your go-to resource for unraveling the complexities of API testing, offering insights, tips, and best practices. Whether you’re a seasoned QA engineer, a developer honing your testing skills, or a tech enthusiast eager to explore APIs, we’ve got you covered. API testing, with its unique challenges like statelessness and diverse endpoints, becomes a powerful asset when approached right. Join in to master the art of API testing and ensure flawless application performance.

Types of Response Codes to Verify: 

Response codes are three-digit numbers sent by web servers to indicate the status of a client’s request. They are part of the HTTP (Hypertext Transfer Protocol) protocol and are used to communicate various outcomes of a request. Here’s a list of response codes, we generally encounter

2xx Success: 

  • 200 OK – The request was successful, and the server has returned the requested data. 
  • 201 Created – The request has been fulfilled, and a new resource has been created as a result. 
  • 202 Accepted – The request has been accepted for processing, but the processing is not yet complete. 
  • 204 No Content – The request was successful, but there is no data to return (e.g., after a successful DELETE request). 


3xx Redirection: 

  • 301 Moved Permanently – The requested resource has been permanently moved to a different URL. 
  • 302 Found – The requested resource is temporarily available at a different URL. 
  • 304 Not Modified – The client’s cached version of the requested resource is up to date, and there is no need to re-download it. 


4xx Client Errors: 

  • 400 Bad Request – The server could not understand the request due to client error or malformed syntax. 
  • 401 Unauthorized – Authentication is required, and the client has not provided valid credentials. 
  • 403 Forbidden – The server understood the request, but the client does not have permission to access the requested resource.
  • 404 Not Found – The requested resource could not be found on the server. 


5xx Server Errors: 

  • 500 Internal Server Error – A generic error message indicating a problem on the server’s side. 
  • 501 Not Implemented – The server does not support the functionality required to fulfill the request. 
  • 502 Bad Gateway – The server, while acting as a gateway or proxy, received an invalid response from the upstream server. 
  • 503 Service Unavailable – The server is currently unable to handle the request due to temporary overloading or maintenance. 
  • 504 Gateway Timeout – The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server. 


Types of Bugs Found During API Testing:

API testing is designed to identify and resolve bugs that may hinder the proper functioning of APIs. Understanding these bug types is crucial for delivering a reliable API service. 


  1. Duplicate Functionality
    Duplicate functionality bugs occur when multiple APIs serve the same purpose or function. Having multiple APIs that perform the same task leads to confusion and inefficiency for developers and users alike. It can also result in redundant code and additional maintenance efforts. Identifying and eliminating duplicate functionality streamlines the API landscape, making it more manageable and cost-effective.
  2.  Missing Functionality
    APIs are designed to fulfill specific requirements and tasks. Missing functionality bugs arise when APIs fail to deliver on those requirements, leaving users unsatisfied and hindering the seamless operation of applications. Detecting and resolving these bugs is crucial to ensure that APIs offer all the expected functionalities and meet user expectations. 
  3. Compatibility Issues Compatibility issues occur when APIs do not integrate well with platforms, frameworks, or programming languages they are supposed to support. Incompatibility can lead to integration problems, errors, and unpredictable behavior. Ensuring seamless integration across different environments is essential for providing a consistent experience to users and developers.
  4. Error Handling Problems
    Error handling is a critical aspect of APIs. When an API receives invalid requests, it should respond with appropriate error messages that help developers identify the issue and take corrective actions. Error handling problems can occur when APIs provide incorrect or inadequate error messages, making it challenging to troubleshoot and debug issues effectively. 
  5. Security Vulnerabilities
    APIs are potential targets for cyberattacks, making security a top priority. Security vulnerabilities may allow unauthorized access to sensitive data or unauthorized operations on the API. Identifying and rectifying security flaws is paramount to safeguarding data and maintaining the trust of users and partners.
  6. Reliability Concerns
    APIs need to be available and accessible at all times to ensure a seamless user experience. Reliability concerns arise when APIs suffer from downtime or intermittent outages. API testing helps in identifying weak points and bottlenecks, allowing developers to enhance the overall reliability and availability of APIs. 
  7. Performance Bottlenecks
    APIs must be able to handle heavy loads and respond promptly to requests. Performance bottlenecks occur when APIs exhibit slow response times, impacting user experience and application performance. API testing helps to identify these bottlenecks, allowing developers to optimize API performance and responsiveness.
  8. Documentation Challenges
    Comprehensive and clear documentation is vital for developers to understand and use APIs effectively. Documentation challenges arise when APIs lack proper documentation, making it difficult for developers to integrate the API into their applications. Clear and user-friendly documentation ensures smooth adoption and reduces the time required for integration.


In conclusion, API testing plays a vital role in modern software development. By addressing various bug types, ensuring security, optimizing performance, and offering clear documentation, developers can enhance the reliability and user experience of their applications. Embracing API testing as an integral part of the development process is the key to crafting robust and efficient APIs that stand the test of time. 

Tags :

APIs APITesting DeveloperTips SoftwareTesting TechEnthusiasts TestingStrategies
Quick Support

Why Do You Wait?

We don't see any reason to wait to contact us. If you have any, let's discuss them and try to solve them together. You can make us a quick call or simply leave a message in our chat. We assure an immediate and positive response.

Call Us

Questions about our services or pricing? Call for support

contact +91 70165-02108 contact +91 99041-54240

Chat Us

Our support will help you from  24*7

chat Live chat now

Fill out the form and we'll be in touch as soon as possible.