Setting variables in scripts in Postman - Build an Automation Script

Set and use environment and global variables in Postman scripts

Preconditions (3)

Step 1: Open the Postman request

Step 2: Go to the Pre-request Script tab

Step 3: Set an environment variable named 'userId' with value '12345' using pm.environment.set()

Step 4: Set a global variable named 'authToken' with value 'abcdef' using pm.globals.set()

Step 5: Send the request

Step 6: Go to the Tests tab

Step 7: Write a script to retrieve 'userId' and 'authToken' variables using pm.environment.get() and pm.globals.get()

Step 8: Use pm.test() to assert that 'userId' equals '12345'

Step 9: Use pm.test() to assert that 'authToken' equals 'abcdef'

✅ Expected Result: The environment variable 'userId' and global variable 'authToken' are set before the request. After the request, the tests pass confirming the variables have the expected values.

Automation Requirements - Postman Sandbox scripting

Assertions Needed:

Assert environment variable 'userId' equals '12345'

Assert global variable 'authToken' equals 'abcdef'

Best Practices:

Use pm.environment.set() and pm.globals.set() to set variables

Use pm.environment.get() and pm.globals.get() to retrieve variables

Use pm.test() with descriptive messages for assertions

Keep scripts clear and simple for maintainability

Automated Solution

Postman

// Pre-request Script
pm.environment.set('userId', '12345');
pm.globals.set('authToken', 'abcdef');

// Tests Script
const userId = pm.environment.get('userId');
const authToken = pm.globals.get('authToken');

pm.test('Environment variable userId is set correctly', () => {
    pm.expect(userId).to.eql('12345');
});

pm.test('Global variable authToken is set correctly', () => {
    pm.expect(authToken).to.eql('abcdef');
});

In the Pre-request Script, we set the environment variable userId and the global variable authToken using pm.environment.set() and pm.globals.set(). This ensures these variables are available before the request runs.

In the Tests Script, we retrieve these variables using pm.environment.get() and pm.globals.get(). Then, we use pm.test() with clear messages to assert that the variables have the expected values. This confirms the variables were set correctly.

This approach keeps scripts simple and easy to understand, which is important for maintaining tests over time.

Common Mistakes - 3 Pitfalls

Using pm.variables.set() instead of pm.environment.set() or pm.globals.set() for setting environment or global variables

Trying to access variables before setting them

Not using pm.test() for assertions and instead using console.log() only

Bonus Challenge

Now add data-driven testing by setting 'userId' and 'authToken' with three different pairs of values in separate requests

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