Collection variables in Postman - Build an Automation Script

Verify usage of collection variables in Postman requests

Preconditions (3)

Step 1: Open the 'User API Tests' collection

Step 2: Create a new GET request named 'Get User Info'

Step 3: Set the request URL to '{{baseUrl}}/users/123'

Step 4: Send the request

Step 5: Verify the response status code is 200

Step 6: Verify the response body contains a field 'id' with value 123

✅ Expected Result: The request uses the collection variable 'baseUrl' correctly, the response status code is 200, and the response body contains the user id 123

Automation Requirements - Postman/Newman

Assertions Needed:

Response status code is 200

Response body contains 'id' field with value 123

Best Practices:

Use pm.collectionVariables.get() to access collection variables

Use pm.test() for assertions

Avoid hardcoding URLs; use collection variables instead

Use descriptive test names

Automated Solution

Postman

pm.test('Status code is 200', function () {
    pm.response.to.have.status(200);
});

const userId = 123;
const responseJson = pm.response.json();
pm.test(`Response has user id ${userId}`, function () {
    pm.expect(responseJson.id).to.eql(userId);
});

The first test checks that the response status code is 200 using pm.response.to.have.status(200). This confirms the request was successful.

Next, we parse the response body as JSON with pm.response.json(). We then assert that the id field in the response equals the expected user id (123) using pm.expect().to.eql().

We use pm.test() to group assertions with descriptive names, making the test report clear.

The request URL uses the collection variable {{baseUrl}} to avoid hardcoding the API base URL, which improves maintainability.

Common Mistakes - 3 Pitfalls

Hardcoding the API URL instead of using collection variables

{'mistake': 'Not using pm.test() for assertions', 'why_bad': "Without pm.test(), assertions won't be reported properly in the test results.", 'correct_approach': 'Wrap assertions inside pm.test() with descriptive names for clear test reports.'}

{'mistake': 'Accessing variables incorrectly (e.g., using environment variables instead of collection variables)', 'why_bad': 'This can cause tests to fail if the wrong variable scope is used.', 'correct_approach': "Use pm.collectionVariables.get('variableName') to access collection variables explicitly."}

Bonus Challenge

Now add data-driven testing by running the same request for user IDs 101, 123, and 150 using collection variables

Show Hint