Dynamic URL building in Postman - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Dynamic URL Variables in Postman

In Postman, you want to create a dynamic URL that changes based on environment variables. Which of the following URL formats correctly uses environment variables to build a dynamic URL?

A https://{{baseUrl}}/api/{{version}}/users

B https://baseUrl/api/version/users

C https://${baseUrl}/api/${version}/users

D https://[baseUrl]/api/[version]/users

💡 Hint

Postman uses double curly braces to reference variables in URLs.

Postman uses the syntax {{variableName}} to insert environment or collection variables dynamically into URLs. Options A, B, and C use incorrect syntax, while D is correct.

❓ Predict Output

intermediate

Output of URL Construction with Pre-request Script

Given the following Postman pre-request script, what will be the final URL used in the request if the environment variable userId is set to 42?

pm.environment.set('userId', '42');
pm.variables.set('endpoint', `/users/${pm.environment.get('userId')}`);

The request URL is set as: https://api.example.com{{endpoint}}

A https://api.example.com/users/42

B https://api.example.com/users/${userId}

C https://api.example.com{{endpoint}}

D https://api.example.com/users/pm.environment.get('userId')

💡 Hint

Variables set with pm.variables.set can be used with double curly braces in the URL.

The pre-request script sets the variable endpoint to /users/42. Using {{endpoint}} in the URL replaces it with this value, resulting in https://api.example.com/users/42.

❓ assertion

advanced

Validating Dynamic URL Components in Tests

You want to write a test in Postman to check that the request URL contains the correct user ID dynamically. Which assertion correctly verifies that the URL includes the user ID stored in the environment variable userId?

Postman

const userId = pm.environment.get('userId');
const url = pm.request.url.toString();

A pm.test('URL contains userId', () => pm.expect(url).to.equal(userId));

B pm.test('URL contains userId', () => pm.expect(url).to.include(userId));

C pm.test('URL contains userId', () => pm.expect(url).to.have.property(userId));

D pm.test('URL contains userId', () => pm.expect(url).to.be.true(userId));

💡 Hint

Check if the URL string includes the userId substring.

The to.include assertion checks if the URL string contains the userId anywhere inside it. Other options misuse assertion methods.

🔧 Debug

advanced

Debugging Incorrect URL Variable Substitution

In Postman, the request URL is set as https://api.example.com/{{endpoint}}. The pre-request script sets pm.environment.set('endpoint', '/users/123'). However, the request is sent to https://api.example.com/%7B%7Bendpoint%7D%7D instead of https://api.example.com/users/123. What is the most likely cause?

A The URL should use single curly braces instead of double curly braces for variables.

B The variable <code>endpoint</code> is set using pm.environment.set but should use pm.variables.set.

C The variable <code>endpoint</code> is set in environment but the active environment is not selected.

D The variable <code>endpoint</code> contains invalid characters that prevent substitution.

💡 Hint

Check if the environment with the variable is active in Postman.

If the environment with the variable endpoint is not selected as active, Postman does not substitute the variable and sends the raw string with encoded braces.

❓ framework

expert

Best Practice for Dynamic URL Building in Postman Collections

When designing a Postman collection to test multiple API versions dynamically, which approach best supports maintainability and flexibility for dynamic URL building?

A Use pre-request scripts to concatenate strings and set the full URL dynamically for each request.

B Hardcode the full URL in each request and duplicate requests for each API version.

C Use global variables for all URL parts and update them manually before each run.

D Use environment variables for base URL and API version, and reference them in the request URLs with {{baseUrl}} and {{apiVersion}}.

💡 Hint

Consider ease of updating and reusability across requests.

Using environment variables for base URL and API version allows easy switching between versions and environments without changing each request. Hardcoding or manual updates reduce maintainability. Pre-request scripts for full URL building add complexity and reduce clarity.