Saving responses in Postman - Build an Automation Script

Save API response to environment variable

Preconditions (2)

Step 1: Open Postman and create a new GET request to 'https://jsonplaceholder.typicode.com/todos/1'

Step 2: Send the request

Step 3: In the Tests tab, write a script to save the 'title' field from the JSON response to an environment variable named 'todoTitle'

Step 4: Save the request

Step 5: Send the request again

Step 6: Verify that the environment variable 'todoTitle' is set with the value from the response

✅ Expected Result: The environment variable 'todoTitle' contains the 'title' value from the API response after the request is sent

Automation Requirements - Postman Tests (JavaScript)

Assertions Needed:

Verify response status code is 200

Verify response body contains 'title' field

Verify environment variable 'todoTitle' is set with correct value

Best Practices:

Use pm.response.json() to parse JSON response

Use pm.environment.set() to save variables

Use pm.test() for assertions

Keep test scripts clear and simple

Automated Solution

Postman

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

const responseJson = pm.response.json();

pm.test('Response has title field', () => {
    pm.expect(responseJson).to.have.property('title');
});

pm.environment.set('todoTitle', responseJson.title);

pm.test('Environment variable todoTitle is set', () => {
    const savedTitle = pm.environment.get('todoTitle');
    pm.expect(savedTitle).to.eql(responseJson.title);
});

This script runs after the API response is received in Postman.

First, it checks the status code is 200 to confirm the request succeeded.

Then it parses the JSON response using pm.response.json().

It asserts that the response contains a title field.

Next, it saves the title value to an environment variable called todoTitle using pm.environment.set().

Finally, it verifies that the environment variable was set correctly by comparing it to the response value.

This approach ensures the response data is saved and can be reused in other requests or tests.

Common Mistakes - 3 Pitfalls

Not parsing the response JSON before accessing fields

{'mistake': 'Using pm.variables.set() instead of pm.environment.set() when intending to save environment variables', 'why_bad': "pm.variables.set() sets variables only for the current request scope, not environment scope, so the variable won't persist.", 'correct_approach': 'Use pm.environment.set() to save variables that persist across requests.'}

Not adding assertions to verify the response status code

Bonus Challenge

Now add data-driven testing by saving the 'title' field from three different todo items (ids 1, 2, and 3) into separate environment variables.

Show Hint