Getting Started With Rest API Testing | Complete Overview

Getting Started With Rest API Testing | Complete Overview

Interestingly, there are many methods used to learn how to test REST API sequences. This REST API testing tutorial will give you the steps needed to test this popular application programming interface. Let’s dive into some of the top solutions you can use for your project.

What Is API Testing?

API testing is essential when developing software, as it tests several key indicators during the development process. API testing is usually conducted through the API itself or alongside integration testing.

The application’s logic, security, and data responses will be analyzed during testing by making requests for testing API endpoints and comparing the response body to the results expected by the dev team.

Developers will analyze a program’s API (Application Program Interface) to ensure it fulfills its expectations. This includes functionality, performance, security, and reliability for most developers. Aside from developers, API testing is commonplace for DevOps managers and quality assurance (QA) personnel. It should be a must-have component of a continuous testing strategy.

What Is REST API Testing?

REST API Testing

REST API testing is the most popular web API because it offers faster communication between RESTful web apps.

It’s because nearly 80% of public web APIs are built on RESTful. You’ll find these APIs typically communicate through HTTP using languages like JSON, HTML, XLT, and XML format, with JSON being the most common.

As per Uday Tank, owner of Rankwisely, REST APIs are an excellent solution for instances where multiple users and different data formats are used when processing commands. As web apps become increasingly complex, REST APIs are highly adaptable and reliable, making them ideal for IoT and eCommerce industries.

Types of API Methods

When using REST APIs, there are four different HTTP methods that it will use to request a command, which include:


GET is primarily used to get server information using a URI (Uniform Resource Identifier). GET is specifically designed not to affect the data; instead, it extracts information to be used.


POST is required to create new entities and to communicate information through a server. For example, POST would share file uploads and customer information. These conversations occur through HTML.


With PUT, it’s a process used to create new entities.

It’s also valuable for editing/updating existing entities.


The final process of REST APIs is DELETE, which does as its name suggests. With DELETE, you can remove pre-existing depictions of target resources transferred by the URI.

How to Test a REST API

How to Test a REST API

Two primary solutions for testing REST APIs are manual and RESTful API automation testing.

Before we get into the below steps, keep in mind you’ll need two components, namely:

  • Code that will test the sample REST API (written by the tester)

  • A framework or tool to work the sample REST API

The three most common options for tools that you can use to test REST API cases include:

  • Curl (LINUX)

  • Postman (REST Client)

  • Advanced REST Client

Steps for Testing REST API

We’ll use Advanced REST Client to test your REST API for this guide. The general steps you need to take are the following:

Step 1: Get Advanced REST Client

First, you must download Advanced REST through Google Chrome’s web store. Once installed, you can launch the ARC (Advanced REST Client) to learn how to test a REST API.

Step 2: Enter Your Information

For the second step, you will need to enter the sample URL for your REST API into the “Request URL” field. Next, choose the method for testing from the drop-down list of HTTP methods available for API testing (ex., POST).

Step 3: Enter and Confirm the Headers Set

You’ll now want to enter your Headers Set under the “Headers” tab by clicking “Insert Headers Set.” Make sure you confirm the data in your headers textbox, and once approved, click “USE THIS SET.”

Step 4: Enter the Body Content

Moving onto step four, you’ll want to click the “Body” tab, which will show more blank fields.

At this point, you’ll need to set the specific body content type you want and the editor view you’re interested in. For example, Application/JSON is your body content type, and raw input is your editor view.

Under the “Payload” heading, set the request body of your demo API in key-value pairs.

When working with POST API, you’ll need to pass standard parameters or body, which you can add under “Payload.”

Step 5: Start the Test

Now that you’ve entered all the information correctly click “Send,” which will begin the testing process. You can also navigate to “DETAILS” to look at the response details of your testing.

Step 6: Review the Results


One of the most important steps of API testing is to make sure you review the results of your testing. These results will include your response message, response body, and response code.

A few examples of response codes include:

  • 305: Use Proxy
  • 510: Not Extended
  • 414: Request URI Too Long
  • 206: Partial Content
  • 499: Client Closed Request (Nginx)

Types of REST API Tests

Let’s dive into the different types of REST API performance tests you can consider using for your project.

Unit Testing

Unit testing helps to check the functionality of separate operations.

Integration Testing

With integration testing in your REST API tests, you’ll check how different software modules interact.

Functional Testing

Functional testing is required to check the REST APIs are behaving correctly.

Load Testing

With load testing, you can look at how many REST APIs can manage combinations for calls.

Reliability Testing

Reliability testing ensures the REST APIs create consistent connections and results.

Security Testing

As expected, security testing checks the validity of the REST API encryption and how access control is managed.

Challenges for API Testing

The complexity of REST APIs is what makes them challenging to secure. They can be hard to reach with endless parameter value combinations and consistent communication with dozens of other systems.

Checking vulnerabilities in REST APIs is like trying to find a needle in a haystack.

Let’s review a few other challenges you’ll likely experience when testing REST API.

Securing REST API Parameter Combinations

REST APIs are crafted with several parameters, including query parameters, request methods, and request URIs. With these parameters, you can have endless combinations that need to be tested, especially as some combinations lead to incorrect program states.

Validating REST API Parameters

Other errors in your testing can occur when you work through the validating process of your REST API parameters. It’s highly challenging because wrong data types and parameter data can pop up.

Some of these data might appear outside of your predefined range of values.

Maintaining the Data Formatting Schema

Maintaining the data formatting schema is particularly difficult when testing REST APIs because the formatting has to be added every time new parameters are included. Considering the data formatting schema is responsible for how the REST API handles requests and responses, it’s an invaluable step.

Testing REST API Call Sequences

To prevent testing errors, your testing team must ensure your successive calls are brought in the right order. With REST APIs, this is of particular importance because they’re usually multithreaded.

REST API Testing Set-Up

Your REST testing setup is challenging because it requires many manual steps. That is particularly true if you’re working on large projects.

To help avoid these challenges, it can always be best to use enterprise-level testing platforms, which help speed up your initial set-up steps.

Reporting Errors for REST APIs

If you’re using black box testing tools, you’ll find it more complicated to manage reporting errors for REST APIs. That is because these testing tools have an unknown number of tested parameter combinations.

As an alternative, you can use coverage-guided testing to ensure you have the most meaningful testing parameters and accurate error reports.

Enhancing Security Through Automated REST API Testing Tools

Security is an essential part of automated REST API testing tools. This is because the issues that arise from exploited security vulnerabilities can significantly affect the usability and functionality of the program.

That said, security testing is one of the most challenging aspects of REST APIs because of their connectivity options and complexity.

It is best to find an API tester designed for testing API endpoints. With this help, all of your relevant parameter combinations will be covered.

Also, it helps to avoid the painstakingly long process of manually testing the security, which can lead to some instances and vulnerabilities being accidentally ignored.

Rest API Testing Tutorial Summary

All of the steps in this REST API testing tutorial will help you check for vulnerabilities across any API application. From checking code from scratch to basic test scenarios, you’ll be able to guarantee all your web apps are in working order before publishing.

As one of the most popular APIs, knowing how to test REST APIs is a must-have for modern devs.

Frequently Asked Questions

1. Which is the best REST API Test Tool?

Testsigma is often regarded as the best REST API test tool because it offers several valuable automated processes.

With the help of the intuitive platform, everyone on your team can easily automate their testing steps from day one. You’ll also find it seamlessly integrates with your existing functional tests.

There are many valuable benefits to REST API automation testing Testsigma offers, including:

  • Easy Setup: One of the most valuable benefits of this platform is that no coding is required during the setup process. You’ll no longer have to worry about creating your environments; simply sign up and begin automating your REST testing.

  • Automated Sequences: The most intuitive feature of Testsigma is that it makes automating your API sequences seamless. You can customize your call sequences to match the workflow of your application, avoiding unexpected and frustrating errors.

  • Built-in End-to-End Testing: Testsigma boasts unified end-to-end testing along with its REST API testing automation. You’ll be able to add functional UI testing to your process, ensuring your application is good to go across the board.

A few other common benefits of the REST API automation of Testsigma include the following:

  • API response body data are automatically stored and available to be reused.

  • Different comparison modes are available to help validate API response messages.

  • You’ll have REST API automation testing for parameters.

  • All API methods can be tested continuously.

2. Is REST API and API testing the same?

REST API and an API test online are different, with several key differences regarding structure, design, protocol, support, and more.

One difference between REST API and APIs is REST API is designed to operate strictly on separate Client and Server web concepts, offering more flexibility. You’ll also find they’re far more complex than APIs, as they communicate over several systems and develop a challenging architecture.

Another massive difference between a REST client extension and APIs is their primary goal. APIs exchange standard data between web services, while REST API interacts with web services through HTTP protocols.

Uniquely, it was developed in 2000 by Roy Fielding, a computer scientist, and remains the standard for public APIs.

3. What are the 3 components of a RESTful API?

There are numerous key components to a RESTful testing API, including:

  • Resources
  • Request Verbs
  • Request Headers
  • Request Body
  • Reaction Body
  • Response Status Codes

4. Why is REST API used?

There are three main benefits to REST API that make it as popular as it is including:

  • Lightweight: A major benefit of a REST API test online is that the API is lightweight and fast, perfect for mobile app projects and IoT devices. As they rely on the HTTP standard, you can use lightweight languages.

  • Independence: With REST APIs, you’ll have a client and server independent of one another. This allows developers to work on different aspects independently, which is especially beneficial when considering RESTful API automation.

  • Flexible: The third notable benefit you’ll find with RESTful testing is its flexibility and scalability. They can be scaled quickly because the server and client are separate. Devs can also integrate REST APIs with less effort.

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