Local variables in Postman - Build an Automation Script

Verify usage of local variables in Postman test script

Preconditions (2)

Step 1: Open the GET request in Postman

Step 2: Go to the Tests tab

Step 3: Declare a local variable named 'responseTime' and assign it the value of pm.response.responseTime

Step 4: Write an assertion to check that 'responseTime' is less than 2000 milliseconds

Step 5: Send the request

Step 6: Observe the test results

✅ Expected Result: The test passes if the response time is less than 2000 ms, confirming the local variable 'responseTime' was correctly used in the test script

Automation Requirements - Postman Sandbox JavaScript

Assertions Needed:

Assert that the local variable 'responseTime' is less than 2000

Best Practices:

Use local variables inside the test script scope

Use pm.response object to access response details

Use pm.test and pm.expect for assertions

Automated Solution

Postman

pm.test('Response time is less than 2000ms', () => {
    let responseTime = pm.response.responseTime;
    pm.expect(responseTime).to.be.below(2000);
});

This test script declares a local variable responseTime inside the test function. It assigns the response time from pm.response.responseTime. Then it asserts that this value is below 2000 milliseconds using pm.expect. This shows how to use local variables in Postman test scripts to store and reuse response data within the test scope.

Common Mistakes - 3 Pitfalls

Declaring variables outside the test function and expecting them to persist across requests

Using global or environment variables instead of local variables for temporary data

Not using pm.expect for assertions and instead using console.log to check values

Bonus Challenge

Now add tests to check that the response status code is 200 and the response time is less than 2000ms using local variables

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