Token management in variables in Postman - Test Execution Trace

Test Overview

This test automates the process of obtaining an authentication token from an API and storing it in a Postman environment variable. It then verifies that the token is correctly saved for use in subsequent requests.

Test Code - Postman Tests

Postman

pm.test("Get Auth Token and save to environment variable", function () {
    pm.sendRequest({
        url: pm.environment.get("auth_url"),
        method: 'POST',
        header: {
            'Content-Type': 'application/json'
        },
        body: {
            mode: 'raw',
            raw: JSON.stringify({
                username: pm.environment.get("username"),
                password: pm.environment.get("password")
            })
        }
    }, function (err, res) {
        pm.expect(err).to.equal(null);
        pm.expect(res).to.have.property('code', 200);
        const jsonData = res.json();
        pm.expect(jsonData).to.have.property('token');
        pm.environment.set("auth_token", jsonData.token);
        pm.expect(pm.environment.get("auth_token")).to.be.a('string').and.not.empty;
    });
});

Execution Trace - 4 Steps

Step	Action	System State	Assertion	Result
1	Test starts and sends POST request to authentication URL with username and password from environment variables	Postman sends HTTP POST request to the API endpoint defined in 'auth_url' environment variable with JSON body containing username and password	—	PASS
2	Receives response from API	API responds with HTTP status code 200 and JSON body containing a 'token' field	Check that error is null and response code is 200	PASS
3	Parse JSON response and verify 'token' field exists	Response JSON parsed successfully and contains 'token' key	Assert that 'token' property exists in response JSON	PASS
4	Save the token value to environment variable 'auth_token'	Environment variable 'auth_token' is set with the token string	Verify 'auth_token' environment variable is a non-empty string	PASS

Failure Scenario

Failing Condition: API returns error or no token in response, or environment variable fails to set

Execution Trace Quiz - 3 Questions

What does the test verify immediately after receiving the API response?

A That the response status code is 200 and there is no error

B That the token is saved in local storage

C That the username and password are correct

D That the environment variable 'auth_url' is set

Key Result

Always verify that tokens received from authentication APIs are correctly saved in environment variables for reuse in subsequent API calls. This ensures smooth and secure token management in automated tests.

Practice

1. In Postman, why is it useful to store an authentication token in an environment variable?

easy

A. To make the token visible to all users of the Postman app

B. To encrypt the token for security

C. To automatically refresh the token without any scripting

D. To reuse the token across multiple requests without re-authenticating each time

Solution

1. Step 1: Understand token reuse in Postman

   Storing a token in an environment variable allows multiple requests to access it easily without needing to get a new token each time.

2. Step 2: Evaluate other options

   Making the token visible to all users or automatic refresh without scripting is not true by default. Encryption is not automatic either.

3. Final Answer:

   To reuse the token across multiple requests without re-authenticating each time -> Option D

4. Quick Check:

   Token reuse = B [OK]

Hint: Tokens stored in variables enable reuse across requests [OK]

Common Mistakes:

• Thinking tokens auto-refresh without scripts
• Assuming variables encrypt tokens automatically
• Believing tokens are shared with all users by default

2. Which of the following is the correct way to set a token value to an environment variable in Postman test script?

easy

A. pm.environment.set('token', response.token);

B. pm.setEnvironmentVariable('token', response.token);

C. pm.environment.token = response.token;

D. pm.variables.set('token', response.token);

Solution

1. Step 1: Identify the current Postman syntax for setting environment variables

   The correct method is pm.environment.set('variableName', value) in Postman scripts.

2. Step 2: Check other options for correctness

   pm.setEnvironmentVariable is deprecated, direct assignment is invalid, and pm.variables.set sets local variables, not environment variables.

3. Final Answer:

   pm.environment.set('token', response.token); -> Option A

4. Quick Check:

   Use pm.environment.set() to set env variables [OK]

Hint: Use pm.environment.set('name', value) to set env variables [OK]

Common Mistakes:

• Using deprecated pm.setEnvironmentVariable method
• Trying to assign variables directly like pm.environment.token
• Confusing local and environment variables

3. Given this Postman test script snippet after a login request:

let jsonData = pm.response.json();
pm.environment.set('authToken', jsonData.token);

What will be the value of {{authToken}} in the next request if the response JSON is {"token": "abc123"}?

medium

A. null

B. undefined

C. "abc123"

D. pm.response.json()

Solution

1. Step 1: Extract token from response JSON

   The script gets the token value "abc123" from the response JSON using pm.response.json().token.

2. Step 2: Set environment variable 'authToken'

   The token value "abc123" is stored in the environment variable 'authToken' using pm.environment.set.

3. Final Answer:

   "abc123" -> Option C

4. Quick Check:

   Stored token = "abc123" [OK]

Hint: Stored token equals JSON token value from response [OK]

Common Mistakes:

• Assuming variable is undefined if not explicitly declared
• Confusing variable name with function call
• Expecting null instead of actual token string

4. You wrote this test script to save a token:

let jsonData = pm.response.json();
pm.environment.set('token', jsonData.authToken);

But the token is not saved. What is the most likely reason?

medium

A. You must use pm.variables.set instead

B. The response JSON does not have a key named 'authToken'

C. pm.environment.set is deprecated and does not work

D. Tokens cannot be saved in environment variables

Solution

1. Step 1: Check the JSON key used in script

   The script tries to access jsonData.authToken, so the response must have that key.

2. Step 2: Verify if the response JSON contains 'authToken'

   If the response uses a different key like 'token', jsonData.authToken will be undefined and nothing is saved.

3. Final Answer:

   The response JSON does not have a key named 'authToken' -> Option B

4. Quick Check:

   Key mismatch causes undefined token [OK]

Hint: Check JSON key names match exactly in script [OK]

Common Mistakes:

• Assuming pm.environment.set is deprecated
• Using pm.variables.set for environment variables
• Believing tokens can't be saved in environment variables

5. You want to automatically refresh an expired token in Postman by chaining requests. Which approach correctly manages the token variable for reuse?

hard

A. Use a pre-request script in all requests to check token expiry and request a new token if expired, then update the environment variable

B. Manually update the token variable in Postman UI before each request

C. Store the token in a global variable and never update it

D. Hardcode the token in the request headers and do not use variables

Solution

1. Step 1: Understand token expiry handling

   Tokens expire, so scripts must check expiry and refresh tokens automatically to avoid failures.

2. Step 2: Use pre-request scripts to automate token refresh

   Pre-request scripts can check if the token is expired and call the authentication endpoint to get a new token, then update the environment variable.

3. Step 3: Evaluate other options

   Manual updates are error-prone, global variables without updates cause failures, and hardcoding tokens is insecure and inflexible.

4. Final Answer:

   Use a pre-request script in all requests to check token expiry and request a new token if expired, then update the environment variable -> Option A

5. Quick Check:

   Automate token refresh with pre-request scripts [OK]

Hint: Automate token refresh in pre-request scripts [OK]

Common Mistakes:

• Relying on manual token updates
• Using global variables without refresh logic
• Hardcoding tokens in requests