REST API: the key to effective software development communication

In today’s dynamically changing software development environment, the concept of REST APIs plays an important role in creating reliable, interactive and efficient applications. Whether you’re an experienced developer, tester, architect, or you’re encountering this topic for the first time, it’s important to be clear about what the REST API is and what its purpose. In this article, we will focus on the basic principles, definitions, and importance of REST APIs in today’s world of software engineering.

In the current digital era, where communication between different software components is essential, our mind focuses on the REST API, which is the fundamental building block for this communication. Interestingly, the term “REST” carries multiple layers of meaning and hides a rich history of software architecture development.

What is REST API?

The Representational State Transfer Application Programming Interface (REST API, also known as the RESTful API) is an application programming interface (API or web API) that conforms to the constraints of the REST architectural style and allows interaction with RESTful web services.

What is an API?

An API is a set of definitions and protocols for creating and integrating application software. Sometimes referred to as a contract between the information provider and the information user – it sets out the content required from the consumer (the call) and the content required by the producer (the response). For example, an API design for a weather service could specify that the user enters a postcode and the producer responds with a two-part response, the first being the highest temperature of the day and the second being the lowest temperature of the day.

In other words, if you want to interact with a computer or system to get information or perform a function, the API will help you with what you want to tell the system so it can understand and fulfill the request.

What is REST?

REST is a set of architectural constraints, not a protocol or standard. API developers can implement REST in different ways.

When a client request is made through the REST API, a representation of the resource state is transferred to the requester or endpoint. This information or representation is delivered over HTTP in one of several formats: Javascript Object Notation (JSON), HTML, XLT, Python, PHP, or plain text. JSON is generally the most popular file format to use because, despite its name, it is language independent as well as human and machine readable.


What is the difference between API and REST API? Web APIs often require a higher level of security because they are used by a wider range of users with different purposes. REST APIs are typically designed for internal users and applications and therefore require fewer security protocols.

There is also a difference in protocols, as you can use the web API to communicate with users via HTTP or HTTPS. However, all communication within the REST API is only supported over HTTP.

Another difference is the format, the web API can automatically convert request (request) and response data into various formats including JSON, XML, BSON. On the other hand, the REST API only supports JSON data format and is therefore less flexible.

The topic of web API testing was covered in the article API testing in Cypress.

REST API Testing

There are many important aspects to testing REST APIs:

  1. Functionality: Ensures that the API works according to specifications and expectations. Verifies that individual endpoints respond correctly to different requests.
  2. Performance: tests how well the API handles different load levels. It helps to identify weaknesses and optimise performance.
  3. Security: verifies that the API is resilient to attacks and that authentication and authorization mechanisms are properly implemented.
  4. Reliability: testing helps to identify and eliminate bugs, which improves the reliability and stability of the application.

The following procedures are often used when testing REST APIs:

  • Manual testing: The tester manually calls different endpoints, tracks the answers and verifies their correctness.
  • Automation testing tools: Automated tools, such as Postman, allow you to create automated test scenarios. These scenarios can be run repeatedly and help identify problems quickly.
  • Performance testing: examines how the API handles load and displays its performance under different loads.

There are mainly 4 types of API testing methods: GET, POST, Delete and PUT.

  • GET – This method is used to collect information from the server using a Uniform Resource Identifier (URI). This method only needs to extract information and should not influence the data in any way.
  • POST – This method is used to create new entities as well as send data to the server, such as customer information, file uploads, etc. via HTML forms.
  • PUT – This method is used to update an entity or create a new entity.
  • DELETE – This method is used to delete existing representations of the target resource provided by the URI.


A REST API Tester is a person responsible for evaluating the functionality, performance, and security of the RESTful API. This includes ensuring that the API correctly responds to various HTTP methods (such as GET, POST, PUT, DELETE), correctly handles various data formats (typically JSON or XML), and adequately handles error responses.

Key Responsibilities of a REST API Tester

  1. Design and implementation:
    • Creating test cases that cover a wide range of scenarios including positive, negative and borderline cases.
    • Conduct tests to validate API functionality and behavior.
  2. Automation:
    • Create automated test scripts using tools and programming languages such as Python, Postman or cURL to increase efficiency and repeatability.
    • Automate regression tests to ensure that new updates do not break existing functionality.
  3. Performance Testing:
    • Conduct performance tests to evaluate API response times, throughput, error rates and concurrent user thresholds.
    • Identification of performance risk points and areas for optimization.
  4. Safety testing:
    • Evaluating API security through penetration testing and checking for vulnerabilities such as SQL injection, cross-site scripting (XSS), etc.
  5. Integration testing:
    • Verifying API integration with other third-party systems or services.
    • Ensuring proper data transfer between different components.
  6. Documentation:
    • Creating and maintaining test documentation including test plans, test cases and test progress reports.
Male IT tester types on keyboard in front of two monitors
A Rest API tester also needs to have knowledge of the programming language.

Skills and qualities of a successful REST API tester

  1. Programming skills:
    • Knowledge of Java, Python, or JavaScript programming language for writing automation scripts.
  2. Understanding HTTP and web technologies:
    • Solid understanding of how HTTP works, status codes, headers, and other key concepts.
  3. API Basics:
    • Deep understanding of RESTful API principles, API structure and ability to read and understand API documentation.
  4. Troubleshooting:
    • Ability to identify problems, analyse their causes and propose appropriate solutions.


1. Architecture

REST (Representational State Transfer):

  • It is an architectural style based on the principles of simplicity and directness.
  • It uses standard HTTP methods (GET, POST, PUT, DELETE) to manipulate data.

SOAP (Simple Object Access Protocol):

  • It is a standardized protocol that defines the rules for communication between systems.
  • It is independent of the transport layer and can be used with different protocols (HTTP, SMTP, TCP).

2. Data format


  • It uses different data formats, most commonly JSON or XML.
  • The data is readable and easy to parse.


  • It uses XML to structure the data.
  • It is robust and defines a precise data structure, but XML can be harder to parse.

3. Scalability:


  • It is more scalable because it does not store any state between requests from the client.
  • Each client request contains all the information necessary for its processing.


  • May be less scalable due to state retention between requests from the client.
  • It uses different settings and contexts to store state.

4. Speed:


  • It is often faster because it uses simple and direct HTTP calls.


  • It can be slower due to more complex processing and messages, mainly due to the use of XML.

5. Usability:


  • It is suitable for web services and modern applications, often used in APIs for mobile applications.


  • It is suitable for complex enterprise applications where tight control over transactions and security is required.

WordPress REST API

Creating a REST API in WordPress is an essential step in allowing external applications or services to interact with your WordPress site and manipulate data. WordPress offers a REST API that allows you to access the content and functionality of a WordPress website over the HTTP protocol.

Activating REST API in WordPress:

  1. Login to the admin interface: open a web browser and login to the WordPress admin interface.
  2. To navigate to the API settings, go to “Settings” and select “Reading”.
  3. Check the “Enable API Web Accessibility” option: find the “Enable API Web Accessibility” option and check it.
  4. Save changes: click on the “Save changes” button at the bottom of the page.


Now that the REST API is enabled in your WordPress project, we can show you how to interact with it using Python. For this, we will need a requests library that allows sending HTTP requests.

  1. Install requests: install the requests library using pip:

pip install requests

  1. Python code to get articles:
import requests

url = "http://your-wordpress-site/wp-json/wp/v2/posts"

response = requests.get(url)

if response.status_code == 200:

data = response.json()

for post in data:

print("Title:", post['title']['rendered'])

print("Content:", post['content']['rendered'])



print("Failed to retrieve data. Status code:", response.status_code)

Replace “http://your-wordpress-site” with the URL of your WordPress site.

  1. Running a Python script:

Run the Python script to see a list of headlines and article content on your WordPress site.

This way you can use the REST API in WordPress and integrate it with Python applications. You can create new articles, update existing articles, get information about articles and much more using this interface.

About the author

Michaela Kojnoková

Agile Test Engineer

Po štúdiu informatiky na ŽU a TUKE som sa najviac ponorila do oblasti automatizácie testovania. Okrem toho sa venujem tvorbe webov, databázam, dátovej analytike, umelej inteligencii a strojovému učeniu. Mám rada cestovanie, šport a najviac si užívam čas strávený v prírode s mojimi blízkymi. LinkedIn

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