API Testing using Postman
Application programming interfaces (APIs) play a key role in modern software development by enabling communication and data exchange between different software components. API testing ensures that these interfaces work as expected and provide reliable and efficient interactions. Postman, a popular API development and testing tool, simplifies the API testing process, providing a user-friendly interface and a robust feature set. In this article, we'll explore the basics of API testing using Postman.
What is Postman?
Postman is a popular collaborative API development tool. It provides features for designing, testing, and managing APIs, making the process of working with APIs more efficient. Postman is widely used by developers, testers, and other stakeholders involved in the API development lifecycle.
Postman is available as a desktop software for Windows, macOS, and Linux and in web version. It has both free and paid plans. It paid plans offering additional features such as team collaboration and advanced monitoring capabilities.
Key features of Postman include:
- API Design: Postman allows users to design APIs by creating and organizing requests, defining parameters, and specifying authentication methods. The intuitive interface makes it easy to visualize and structure API endpoints.
- API Testing: Users can create and run automated tests for APIs within the Postman platform. This includes writing test scripts, setting up assertions, and generating reports to ensure that APIs function as intended.
- Collaboration: Postman facilitates collaboration among team members by allowing them to share collections of requests, tests, and environments. Teams can work together on API development projects and easily share updates.
- API Monitoring: Postman can be used to monitor APIs in real-time, providing insights into performance and uptime. It helps in providing issues that impact the end user.
- Automation: Postman supports automation through its command-line interface (CLI) and integrations with popular CI/CD (Continuous Integration/Continuous Deployment) tools. This enables the integration of API testing into the development workflow.
- Environment Management: Postman allows users to define and manage environments, making it easier to switch between different sets of variables, configurations, and credentials for testing against various environments (e.g., development, testing, production).
- Mock Servers: Postman can generate mock servers, allowing developers to simulate the behaviour of an API before it's fully implemented. This is useful for front-end and back-end teams working in parallel.
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What is an API?
An API, or Application Programming Interface, is a set of rules and protocols that allows different applications to communicate with each other. It defines the methods and data formats that applications can use to request and exchange information. APIs are crucial for enabling the integration of different software systems, making it possible for them to work together and share data seamlessly.
Key concepts related to APIs:
- Endpoint: An endpoint is a specific URL or URI (Uniform Resource Identifier) that an API exposes for interacting with its services. Each endpoint represents a specific function or resource within the API.
- Request: A request is made by a client (an application or system) to an API endpoint, asking for a specific operation to be performed. Requests are typically made using HTTP methods such as GET, POST, PUT, or DELETE.
- Response: The API responds to a request with data, often in a specific data format such as JSON (JavaScript Object Notation) or XML (eXtensible Markup Language). The response contains the requested operation's result and any relevant data.
- HTTP Methods: APIs commonly use standard HTTP methods to perform different actions. For example, GET is used to retrieve data, POST is used to submit data, PUT is used to update data, and DELETE is used to remove data.
- Authentication: Many APIs require authentication to ensure that only authorized users or applications can access their services. This can involve the use of API keys, OAuth tokens, or other authentication mechanisms.
- Documentation: API documentation provides detailed information on how to use the API, including the available endpoints, required parameters, expected responses, and any authentication requirements. Well-documented APIs make it easier for developers to integrate and use the API effectively.
- RESTful APIs: REST (Representational State Transfer) is a common architectural style for designing networked applications. APIs that adhere to REST principles are referred to as RESTful APIs. They use standard HTTP methods, follow a client-server model, and are stateless.
- SOAP APIs: SOAP (Simple Object Access Protocol) is a protocol for exchanging structured information in web services. SOAP APIs use XML for message formatting and are known for their strict standards and strong typing.
Now, let's take a working API and test that API using Postman. For this, we use free fake API available on the JSON Placeholder website and test using Postman. We will use the following URL for examples in the Postman
https://jsonplaceholder.typicode.com/posts
Working with GET Request
In the postman workspace
- Set your HTTP request to GET.
- In the request URL, put the above link
- Click the Send button
- You will get 200 OK Status in the response
- 100 post will be in the response body, which shows that the test is run successfully
If the test failed, then the reasons might be like:
- The request URL is invalid
- Due to a bad network or server is down
- Authentication key is required
Working with POST Request
In the postman workspace
- Set your HTTP request to POST.
- In the request URL, put the link we used earlier in the GET request.
- Switch to the Body tab, select Raw, then JSON
- In the body, put the below JSON
[{ "userId": 1, "id": 101, "title": "Api Testing using Postman", "body": "We are testing post request by creating this post on server." }]
- Click Send button
- You will get 201 Created status in the response.
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