Environment variables in Postman are a powerful feature that allows you to manage and reuse values across multiple requests and collections. They help in making your API testing more dynamic and flexible by allowing you to change the values of variables without altering the requests themselves.

1. Environment: A set of key-value pairs that can be used to customize requests. You can create multiple environments for different stages of development (e.g., development, testing, production).

2. Variable: A placeholder for a value that can be reused in requests. Variables can be defined at different scopes: global, collection, environment, and local.

3. Scope Hierarchy: Postman resolves variables in the following order of precedence:

   • Local
   • Data
   • Environment
   • Collection
   • Global

1. Creating an Environment:

   • Open Postman and click on the gear icon in the top-right corner.
   • Select "Manage Environments".
   • Click "Add" to create a new environment.
   • Name your environment (e.g., "Development").
   • Add key-value pairs for the variables you need (e.g., baseUrl, apiKey).

2. Using Variables in Requests:

   • In your request URL, headers, or body, use double curly braces to reference a variable. For example, {{baseUrl}}/api/v1/users.
   • Postman will replace {{baseUrl}} with the value defined in the selected environment.

3. Switching Environments:

   • To switch between environments, click on the environment dropdown in the top-right corner and select the desired environment.

Let's create a simple GET request using environment variables.

• {{baseUrl}}: This variable allows you to change the base URL for all requests by simply updating the environment variable.
• {{apiKey}}: This variable is used to securely manage your API key without hardcoding it into each request.

1. Create an environment named "Testing".
2. Add the following variables:
   • baseUrl: https://api.testing.com
   • userId: 12345
3. Create a GET request to {{baseUrl}}/users/{{userId}}.
4. Send the request and verify the response.

Solution:

• Ensure the "Testing" environment is selected.
• The request URL should resolve to https://api.testing.com/users/12345.

1. Update the userId variable to 67890 in the "Testing" environment.
2. Resend the GET request.
3. Verify that the request URL now resolves to https://api.testing.com/users/67890.

Solution:

• After updating the variable, the request should correctly reflect the new userId.

• Forgetting to Select the Environment: Always ensure the correct environment is selected before sending requests.
• Variable Name Typos: Double-check variable names for typos, as Postman will not replace them if they are incorrect.
• Scope Confusion: Be aware of the variable scope hierarchy to avoid unexpected values being used.

Environment variables in Postman are essential for efficient API testing, allowing you to manage and reuse values across different requests and environments. By mastering environment variables, you can streamline your testing process and adapt quickly to different testing scenarios. In the next module, we will explore more advanced API testing techniques, including chaining requests and using Postman scripts.