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A Guide To REST API Testing Strategy

A Guide to REST API Testing Strategy

Recent studies on customer experience by Zendesk reveal that one bad customer service experience leads to 39% of customers ignoring a company for the next two years. To avoid such incidents, you should shape up your user interface (UI) interactions effectively to engage with the prospects and constantly add value to their interactions with the content on your website. It’s one of the fastest, most convenient ways to prevent massive losses and boost your profits.

Creating an excellent UI is not possible without an Application Program Interface (API) - the intermediary that bridges gaps between programs. One type of API called Representational State Transfer (REST) API can transform businesses of any size or industry by addressing the needs of both companies and consumers. Read on to learn how to use REST API to achieve new heights.


What Is an API?

API is a set of rules for software that validates the capabilities of a new application in terms of performance, operations, and security. It uses rules to enable programs to connect to other files. Developers create APIs on servers to activate communications with clients.

This software intermediary is present in many of our daily tasks. For example, you can witness how API works in sites that offer several login options. If a page shows you options to log in via Facebook, Instagram, or Twitter, it uses an API to provide applications with identification information. In this scenario, the API elevated the customer experience by making the login process convenient and seamless.


What Is REST?

Developers created REST - a software architectural technique for designing networked applications - to guide the development of the World Wide Web. This method focuses on reducing latency and boosting security. Today, many software companies use it as a set of guidelines for creating reliable web services.

REST developers use standard operations with a stateless protocol. This process creates fast, reliable services that allow specialists to reuse REST components. You can update and manage these factors even while a system runs.


What Is a REST API?

A REST API is a type of API that adheres to REST limitations and allows interactions with other sites. Any page that follows REST constraints is informally called RESTful API. Below are some of its core features.

  • A RESTful API is stateless
  • It supports JSON and XML alike
  • It offers simplified implementation versus the standard SOAP
  • Every architectural modification in the REST API should reflect in its documentation
  • It provides developers with an extensive range of error messages

Here’s a REST API example in an e-commerce setting. If you want to purchase affordable running shoes, you use a search engine, type in keywords, and receive a list of options in return. In most cases, the results are relevant to your search. If used correctly, this tool should enhance a client’s experience with your brand.

Before you run tests, here are some guidelines to follow on how to create REST API:

  • Use HTTPS
  • Include a timestamp to requests
  • Limit HTTP methods
  • Apply input validation if necessary
  • Use OAuth
  • Avoid showing sensitive data on URLs
  • Create a security checklist and run tests

2021-2022 Software Development and QA Testing Report


How To Test REST API

The goal of testing REST API is to check individual functions. You need an application to interact with sample APIs, which are activities that require a testing tool and a code.

You can use these tools to test REST API cases:

  • Postman: A scalable instrument that integrates into a CI/CD pipeline
  • Curl in Linux: A command-line mechanism that supports over 20 protocols in transferring data
  • Advanced Rest Client: A method that supports all HTTP methods

API Test Strategy

The API test strategy provides information on individual test scenarios and cases. Below are three core objectives of API functional testing.

  • APIs Ensure Proper Implementation: In software development, complex codes may sometimes lead to bugs. It’s impossible to prevent bugs when building software, but an API can help check a system’s functionalities to detect and fix them.
  • They Ensure that Executions Work as Intended: This API function later becomes your documentation. It provides updates on an API’s lifecycle, including new versions, upgrades, and limitations.
  • They Provide Regressions Between Code Mergers and Releases: The objective of any file is to merge its algorithms with other programs without conflict. However, changes may sometimes cause friction. API enables developers to enhance features seamlessly.

What to Test in an API

APIs are essential in gathering data and implementing processes for customer service improvements. It's a vast, complex field, making it crucial to know what you want to test. This step is essential to avoid getting overwhelmed with all the available information.

Below are some of the most common factors to consider.

  • API Test Actions

    Several test actions make up one API test, making them essential in a test flow. Every API request should include the following:

    1. Verify HTTP Status Code: This step is crucial to quickly finding and fixing broken links. You can create a resource to return un-permitted requests like redirections, client errors, and server errors.
    2. Verify Response Headers: Response headers are HTTP requests that don’t relate to the message. You can use factors like age, location, or server to gain more context about a response. This step is crucial because it affects both the security and performance of your site.
    3. Verify Response Payloads: Apart from letting you see replies from curl or Postman, this action will help you make use of JSON data. The information should include field names, types, values, and errors.
    4. Verify Basic Performance Sanity: Sanity testing makes sure that there are no bugs in the system and that they will not affect code changes. It also checks for the completion speed of any test.
    5. Verify Application State: This action may be optional, but we highly recommend taking it. You can use it for manual testing or when you have access to an interface such as UI.
  • Authorization and Security

    API is a fundamental aspect of any software application, (like healthcare apps, for instance) making it prone to attacks. Many developers use this tool, which means it provides access to sensitive functions and data. It’s crucial to run authorization and security checks to enable safe transactions for your clients.

    1. Check that APIs Follow Proper Security Protocols: Here are four aspects to consider when you’re enhancing your site’s safety: parameter tampering, injection, input fuzzing, and unhandled HTTP systems.
    2. Oversee Role Permissions: You can restrict user access depending on an individual’s job description. Evaluate the responsibilities team members have to determine the resources they need. Don’t permit anybody unnecessary any access that might compromise your program’s security.
    3. Find Data Leaks: Data leakage is the unauthorized information transfer from an internal source to an external destination. Whether it’s intentional or not, it can compromise your reputation, finances, and operations.
  • Performance Tests

    Because of its functions, it’s essential for APIs to be accurate, secure, and reliable. There are many types of API tests, from UI to security and validation testing. In most cases, these tests fall under the performance category because they aim to determine the effectiveness of certain aspects of the site.  They help organizations collect performance data to improve customer experience.

  • Load and Stress Tests

    Software developers perform load tests to evaluate system performance using real-life load conditions. On the other hand, specialists run stress tests to verify a system’s robustness under extreme conditions.

    While the two test types have distinct differences, they both have a common goal. They aim to determine the breaking points of sites and applications to avoid crashes.

  • Usability Tests

    Usability tests, also called user experience tests, measure the user-friendliness of a software. Experts run them to determine and fix defects that hinder seamless consumer operations. Remember to test the entire customer journey when using them, from logging in to authentication and purchase. Any error in the process can lead to lost clients.



In today’s modern era, organizations have to provide their clients with secure and scalable connections between a diverse range of platforms. REST API testing is the only reliable way to achieve this goal. From protecting users from malicious code to maximizing time efficiency, this tool can transform your UI.

As a trusted quality assurance provider for almost 20 years, QASource has grown by as much as 50% annually. We achieve unmatched growth levels because of our groundbreaking services. If you’re ready to take the digital world by storm, request a free quote now. We can’t wait to help you take your business to new heights.


This publication is for informational purposes only and nothing contained in it should be considered legal advice. We expressly disclaim any warranty or responsibility for damages arising out of this information and encourage you to consult with legal counsel regarding your specific needs. We do not undertake any duty to update previously posted materials.