Setting variables from response in Postman - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Extracting a value from JSON response and setting an environment variable

Given the following Postman test script, what will be the value of the environment variable userId after running this test if the response body is {"user": {"id": 42, "name": "Alice"}}?

Postman

const responseJson = pm.response.json();
pm.environment.set("userId", responseJson.user.id);

A undefined

B 42 (number)

C "42" (string)

D null

💡 Hint

Postman environment variables store values as strings.

Postman environment variables always store values as strings, even if you set a number. So setting userId to responseJson.user.id (which is 42) stores it as the string "42".

❓ assertion

intermediate

Validating a variable set from response header

You want to check if the Postman environment variable sessionToken matches the Authorization header value from the response. Which assertion correctly tests this?

Postman

pm.test("Session token matches Authorization header", () => {
    const authHeader = pm.response.headers.get("Authorization");
    const sessionToken = pm.environment.get("sessionToken");
    // Fill in the assertion below
});

A pm.expect(sessionToken).to.equal(authHeader);

B pm.expect(sessionToken).to.be.true;

C pm.expect(sessionToken).to.be(authHeader);

D pm.expect(sessionToken).to.eql(authHeader);

💡 Hint

Use the correct Chai assertion method for equality.

The to.equal() method checks strict equality of values. to.eql() is for deep equality (objects). to.be() is not a valid Chai assertion method. to.be.true checks if the value is boolean true, which is not correct here.

🔧 Debug

advanced

Debugging why a variable is not set from nested JSON response

You run this Postman test script but the environment variable orderId remains undefined. The response body is {"data": {"order": {"id": 1234}}}. What is the bug in the code?

Postman

const jsonData = pm.response.json();
pm.environment.set("orderId", jsonData.order.id);

A orderId variable name is reserved and cannot be set

B pm.environment.set requires a callback function

C pm.response.json() returns a string, not an object

D jsonData.order is undefined because the correct path is jsonData.data.order

💡 Hint

Check the JSON structure carefully.

The response JSON nests order inside data. Accessing jsonData.order returns undefined, so jsonData.order.id causes an error or undefined. The correct path is jsonData.data.order.id.

❓ framework

advanced

Best practice for setting collection variables from response in Postman

Which Postman script snippet correctly sets a collection variable token from a JSON response field access_token and ensures it is available for all requests in the collection?

A

const json = pm.response.json();
pm.collectionVariables.set("token", json.access_token);

B

const json = pm.response.json();
pm.environment.set("token", json.access_token);

C

const json = pm.response.json();
pm.globals.set("token", json.access_token);

D

const json = pm.response.json();
pm.variables.set("token", json.access_token);

💡 Hint

Collection variables are shared across all requests in a collection.

Using pm.collectionVariables.set() sets the variable at the collection level, making it accessible to all requests in that collection. pm.environment.set() sets it only for the current environment. pm.globals.set() sets a global variable, which is broader than collection scope. pm.variables.set() sets a variable only for the current request execution.

🧠 Conceptual

expert

Understanding variable scope precedence in Postman

If a variable named apiUrl exists in globals, environment, collection, and local scopes with different values, which value will Postman use when you call pm.variables.get("apiUrl") inside a request test script?

A The value from the collection scope

B The value from the local scope (set during the current request execution)

C The value from the environment scope

D The value from the global scope

💡 Hint

Postman uses a specific order to resolve variable values.

Postman resolves variables in this order: local (request-level) > data > environment > collection > globals. The pm.variables.get() method returns the first found value in this order. Local scope variables override all others.