Postman Tutorial For Beginners

In this tutorial, you will learn about the Postman testing tool. The Postman testing tool is used for testing APIs(Application Programming Interface) of a software application. As the number of webs and mobile applications increases, API testing is also increasing. So, we have to learn postman testing for testing APIs.

Postman Tutorial for Beginners

In this Postman tutorial, we will start from the basics of Postman and learn all the major Postman concepts that a Postman professional must be aware of. Now, let’s have a look at the components of this tutorial.

• What is Postman?
• What is API
• Why Postman is used
• Advantages of Postman
• How to use Postman
• Postman API Testing
• HTTP Methods

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What is Postman

Postman is a software testing tool used for API Testing. API(Application Programming Interface) enables software applications to interact with each other.

What is API

API is defined as a collection of functions, procedures, and other Access Points that a program or an operating system makes accessible to developers to allow it to communicate with other software applications.

Why Postman is used

Postman is used for API Testing due to the following reasons:

1. Availability

After installing Postman into your system, you can use it anywhere by just logging into your account.

2. Make use of collections.

In Postman, users can create collections for their corresponding API calls. Every collection will create multiple and subfolder requests. This assists in arranging the test suites.

3. Collaboration

Environments and Collections are imported and exported to enhance file sharing.

4. Test Creation

Verification of successful HTTP response status is added to each API for testing checkpoints.

5. Continuous Integration

Postman can support Continuous Integration. Development procedures are carried out according to that.

6. Automation Testing

By using Collection Runner Newman, we can run tests in multiple iterations to reduce the time for iterative tests.

7. Debugging

To Debug the tests efficiently, the postman console assists in monitoring what data has been retrieved

Advantages of Postman

• Postman enables us to create integration test suites easily.
• Postman allows us to save data for other tests.
• Postman supports integration testing.
• Postman can easily integrate with other build tools like Jenkins, etc.
• Postman eases the movement of environments and tests to code repositories.

How to use Postman

The features of Postman are as follows:

1. New: This feature is used to create a unique environment or request.
2. Import: This feature is used for importing a collection or environment.
3. Runner: This feature is used for executing automation tests.
4. Collaboration: This feature is used for inviting team members for interaction.
5. Collections: Collections are created for arranging the test suite.
6. Open New: This feature is used for opening new tabs.  
7. My Workspace: New Workspace is created individually, or as a team.
8. History: This feature is used for displaying past requests.
9. Request Tab: This feature is used for displaying the title of the request.
10. HTTP Request: This feature is used for displaying the dropdown list of various requests.  
11. Params: This feature is used for writing the required parameters for a request.
12. Authorization: To use APIs, appropriate authorization is required.
13. Save: This feature is used to save the changes made to a request.
14. Headers: You can set headers depending upon the requirement of the organization.
15. Pre-request Script: This feature is used for executing the test scripts before requests.

Postman API Testing

After installing Postman Successfully, we can start API Testing by making HTTP requests to the server.

Related Article: Learn API Testing

HTTP Methods

The Hypertext Transfer Protocol is used to allow communication between servers and clients. It acts as a request-response protocol between the client and the server. The web browser is considered a client, and the application that hosts the website is viewed as a server.

The most popular HTTP methods are as follows:

• GET: GET Method is used for retrieving the data from the server through the URI.
• POST: POST request is used to send data to the server.
• PUT: It is used to send data to a server to create/update a resource.
• PATCH: It is used to update partial resources.
• HEAD: HEAD is similar to GET; the only difference is HEAD does not have a response body.
• DELETE: The DELETE Method deletes the mentioned resource.

Testing GET Requests

Let us test the APIs and to test the API we have to make a GET request. The procedure for the GET request is as follows:

• Create a collection in POSTMAN.
• Create a request and save it in a collection.
• Now, we have to pass different parameters to the request to get a response.
• Now we have to enter the URL needed, and then we have to click on the "SEND" button.
• Now we will get a response in the body section indicating that we have tested the API Successfully.

Testing POST Requests

For example, if we want to create a user or delete a Gmail user, we will use the POST method. In the Post request, we will send some data in the request body and API will send data in response to that. 

The procedure for creating a POST Request

• Create a Request and save it in a collection.
• Select POST from the menu.
• Enter the website URL in the request URL.
• Select the "Raw" radio button after clicking on Body Tab.
• After typing the required code, click the send button.
• After checking the response and the status code, we can say that we have successfully tested this API.

Request Parameterization

It is one of the essential features of Postman. Rather than making the same requests with different data, we can use variables for parameters. Parameterization helps in avoiding the repetition of similar tests. 

Steps to be followed for creating parameterized get request

• Establish the HTTP Request as getting.
• Give any URL as an Input link. Substitute the first part of the URL with any parameter.
• Click send and Set the environment to use the parameter.
• Press edit to establish the variable in the global environment to use in all collections.
• Establish the URL and Save it.
• When you see the next screen, click close.

Creating Postman Tests

Postman tests are developed using javascript, and they are included in tests to check results like failed or successful status and expected results comparison.

Steps to be followed for creating Postman Tests

Step 1) First go to Get user request.

Step 2) Move to the test tab.

Step 3) When you go to the snippets section, click on "Status code: Code is 200".

Step 4) When you click send, the test result will be displayed.

Step 5) After returning to the tests tab, we will add another test and compare the expected result with the actual result.

Step 6) In Postman, we can create different types of tests, depending upon the requirement to select the test.

Conclusion

Postman is a freeware testing tool used for testing APIs. As APIs are used for software interaction, testing them is essential before delivering the product. It supports the continuous integration of the development code. It supports every method of the HTTP request so, that we can test any URL.