How to create API tests using Postman

Step 1. Create a collection

Collection is the set of requests which are grouped using specific logic (f.e. by features, different modules, etc.)

To create a collection proceed with the following flow: “New” -> “Collection” -> specify the title for the collection

Each collection could be divided into the separate folders

Create a collection

Step 2. Add a request

Using the “3 dots” menu select “Add request” option. For learning purposes let’s use any open API (f.e. https://api.agify.io/)

Each request contains the following tabs:

• Params — contains parameters for query string
• Authorization — contains necessary authorization data
• Headers-contains particular headers
• Body — contains a set of the values which will be sent in API request
• Pre-request script — set of the manipulation which will be done before sending the request. In some cases, it could be used for token generation or just preconditions
• Tests — this tab is using for tests that cover specific request
• Settings — contains a list of the request configuration

Let’s create a simple GET request using open Agify API (f.e. https://api.agify.io/). It does not require any specific headers or authorization and selected for learning purposes. According to documentation, “name” value is required parameter

To create a GET request:

• Leave default GET method
• Specify “https://api.agify.io/” value within URL field
• Add “name” parameter with any existing name value (f.e. such one — “testName”)

To send a request just click on “Send” button and check the response block

Step 3. Add tests

Step 3.1 Positive tests

Go to “Tests” tab and create a simple check for response status code (it should be 200)

You can use Snippets for quick creation

Snippets

Send request again and pay attention to the “Test Results” tab within the response block

Test results

The other positive tests could be the following:

• Response time is less than 200ms
• The response has a valid structure
• The response has valid data etc.

Positive tests

Step 3.2 Negative tests

As mentioned before Agify API expects “name” parameter. To create simple negative test let’s send GET request without “name” parameter (you can just turn off checkbox for needed parameter). Send the already existing request with cleared (or turned off) “name” parameter to check how existing tests working

Let’s adaptive tests for negative case:

Step 4. Using environments

Environment stores the set of the variables which are using for requests but could have different values on different environments (f.e. develop, staging or preprod). To manage your environment click on “eye” icon at the top left corner

Step 5. Using environment variables

Environment variables store in one place but could be used in any request. the first reason why it necessary to store values as environment variables that there is no need to change variables in every place where they are using when value is changing. Another point is manipulation using these variables — assign new value within test or pre-request script

To use environment variable just put {{name of the variable}} into your request (make sure that correct environment is selected)

To use an environment variable for any manipulations store it from the separate variable using get method

To update environment variable value use set method

Step 6. Runner

To run all existing requests within the specific collection just open the needed collection and click on “Run” button

NOTE: If you updated any request do not forget to save it before starting Runner (Runner uses the latest saved version)

Have a happy API testing!