REST API: understand the step-by-step to perform tests

Before calling an API, you must define input parameters. These parameters pass needed information to the API to enable it to perform its function and therefore are necessary for determining whether the API performs as expected. For example, a REST API can accept header, query, and rest body parameters, among other input parameter types. We can also retrieve values to be used in the future, i.e. we can perform several scripts, depending on your needs. If the data was removed and the delete API is implemented properly, you will see the status code 204 No Content.

  • The point of load testing is to measure where the limit of system performance under high load lies.
  • If one area of the app is being updated, the other areas can continue functioning without interruption.
  • More than once I spent half a day debugging an error in my app, only to notice that a downstream API was borked all along.
  • To accomplish that, the sample application is equipped with TestContainers, a tool that provides a selection of ready to use database instances.
  • From financial services to healthcare and biotech to government and defense and more, we work with our customers to address their specific needs.
  • It is widely used to test JSON and XML based web applications.

We’ll build a suite of parametrized tests that will continue to work over time, not just the first time that you ran it. An important part of this is modifying the environment in a request. That is our way of transmitting parameters between requests.

Validating REST API Parameters

Started as a browser extension for API validation, today with integrated test automation features, Postman is much more than just an HTTP client. QA engineers perform automated API testing using a testing tool that drives the API. We will discuss the most popular solutions in the next section. In the Agile processes, where instant feedback is needed, unit and API testing are preferred over GUI testing as they are quicker to create and easier to maintain. While the latter requires considerable rework to keep pace with frequent change. We’ve also elaborated on the basics of software quality management.

Why should you test REST API

API testing is a type of software testing that analyzes an application program interface to verify it fulfills its expected functionality, security, performance and reliability. The tests are performed either directly on the API or as part of integration testing. An API is middleware code that enables two software programs to communicate with each other.

It will help even more in the case bellow, when we receive a JSON list from the server. Notice the injection of the server port and the setup done in the init. Now, that we told REST-assured about the server details, let’s perform the request.

API testing is critical for automating testing because APIs now serve as the primary interface to application logic. This is also because GUI tests are difficult to maintain with the short release cycles and frequent changes commonly used with Agile software development and DevOps. This means that the core functionality of the system is contained within the “business logic” layer as a series of discrete but connected business components.

Response Assertions in REST API Testing

Once the testing process is completed, you can get the result of those tests every day. If failed tests occur, you can check the outputs and validate issues to have proper solutions. Does the tool support import API/Web service endpoints from WSDL, Swagger, WADL, and other service specifications? However, it will be time-consuming if you have hundreds of APIs to test. Is a standard protocol defined by the W3C standards for sending and receiving web service requests and responses. Because a unit test does test a unit of code, it’s usually fast, and it always should be.

In a nutshell, JSON gives us a human-readable collection of data that we can access in a logical manner. REST is a software architecture style, commonly used for web services. Due to its popularity, you will probably need to load test RESTful APIs at some point. Kotest does provide a friendly way to create data driven tests, from the developer point of view. In Kotlintest, you provide a table with data to be tested and the expected results as well (variables starting with ‘exp’ below). Note that a object pgContainer is used to get the current database port.

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They offer features like creating specifications, mocking, and automated testing. Endpoints have the possibility to accept many combinations of values and data types. This can make it difficult to get the full test coverage that is desired. Determine how often the tests are run, and how are they deployed — with a commercial testing tool or an internally developed tool.

In this endpoint, we are simply checking the value of an HTTP Header supplied against a constant value. If it’s a match we return some data and a successful status code, otherwise, we return an unauthorized response. Obviously in reality our security approach will be more robust than here, using something like JWT and Identity, but for our testing purposes, this will suffice.

I think you’ll be surprised by how intuitive it is to create your tests from new or existing APIs. When determining what to test with an API, it’s helpful to understand the different categories of tests. When testing APIs, test cases can be designed for each endpoint or a group of endpoints that are designed to work together (i.e a functional flow like logging in). Several common practices can help you avoid problems when you’re ready to execute your API tests against the live production server.

The Future of API Testing

This enables them to identify any errors or weaknesses early on in the development process. TestCafe includes a comprehensive set of server-side API testing tools. You can add dedicated API tests to your test suite, or include API testing methods in existing functional tests. Another example is travel booking systems, such as Expedia or Kayak. Users expect all the cheapest flight options for specific dates to be available and displayed to them upon request when using a travel booking system.

The following tutorial is for REST API automation testing using Postman. Postman is a popular API client that allows developers and teams to test, share, create, collaborate, and document the API development process. The client is ideal to create and save the complex, as well as simple HTTP/s requests along with their responses. Postman can be downloaded as a Chrome extension, or you can visit the official website to download the program. 4xx status code error messages typically occur when something happens at the client/browser level.

Creating Basic Endpoints

In this way, you can define edge cases and determine the parameters that are most vulnerable to injection attacks . In addition to the above questions, it is important to have a good understanding of the meaning of passing and failing the test. The engineering requirements and sessions that trigger the attack and send it to the system, preferably inside and outside the network. Imagine you are trying to find an airline that offers inexpensive tickets. You type your request in the search engine, and you get a whole list of companies.

Functionality testing — the API works and does exactly what it’s supposed to do. Once you’ve set up your API testing environment, make an API call right away to make sure nothing is broken before you go forward to start your more thorough testing. Here at, we are committed to making API testing easy and reliable for everyone. We believe that API testing is a crucial part of the API development lifecycle, and that it should not be forgotten. In this example I’ve taken the title of a post at our server.

The best way to monitor and report REST API tests is with coverage-guided testing approaches, as they can provide meaningful coverage and error reports. Now you’re ready to select an API testing tool that can help automate or simplify the API testing process. When evaluating different API testing tools, it’s important to know what kind of API you’ll be testing, what kind of tests you’ll be running, and what your budget is. Next, you need to determine the testing requirements of the API.

API testing is designed to assess the functionality, reliability, performance, and security of an API, and is therefore an essential part of the API development lifecycle. REST Assured is a Java library for creating a REST API testing tool script. So, to get started with it, you’ll have to set up a new Java project first, and then include it as a library for your project. Its documentation is stored inside the Github repository. REST Assured is the best fit for functional testing of REST API services and it requires strong coding skills to create tests. It has a friendly UI for constructing requests and reading responses, which allows for creating automated tests quite fast.

Why should you test REST API

RestSharp’s functionality allows for straightforward test creation, serialization and deserialization. It can handle synchronous and asynchronous requests with a wide list of ready-made authenticators. Uploading files and forms in multiple parts, RestSharp api testing best practices cuts down on upload times. The last step in the security audit tests the API at its absolute limits. Forcibly inputting massive amounts of random data, it tests whether the API will stand it or end up with negative behavior like a forced crash or overflow.

API security tests

Once you develop a suite of functional tests and security tests, you’ll need to execute them on a regular basis. How often you execute the tests depends on your business needs. Daily API testing on production is ideal — better yet, multiple times per day or even continuously. Consider creating a critical test suite for items that require continuous testing, and leave the rest on a daily schedule. Conversely, API testing tools provide user-friendly interfaces with minimal coding requirements that enable less-experienced developers to feasibly deploy the tests.

Instead of banging our head against the wall trying to fix the unfixable, we can mitigate the problem by using lower level tests. The statusText property contains the status text of the HTTP response. Alternatively, you can save the return value of the request method and use assertions later on in the test. Do not enable the withCredentials option for same-origin requests. If Katalon has piqued your curiousity, we have an article with an objective review of this software.

The ability to prototype and preview the HTTP request, with the ability to specify the HTTP headers, body, method and standard HTTP credentials. A common format used in web browser-based APIs is JSON since it returns the data as JavaScript Object Notation objects. These can be used directly in a web browser because they match the format used by JavaScript to store arrays and objects. It is also a very compact format, making it ideal for communications on mobile networks with limited bandwidth. Proficiency testing — the API increases what developers are able to do.


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