Basic authentication in Postman - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What does Basic Authentication encode?

In Basic Authentication, what is the format of the encoded string sent in the Authorization header?

A MD5 hash of the username only

B Base64 encoding of username and password joined by a colon

C Plain text username and password separated by a comma

D SHA256 hash of the password only

💡 Hint

Think about how username and password are combined before encoding.

Basic Authentication sends the username and password joined by a colon, then encoded in Base64. This string is sent in the Authorization header.

❓ Predict Output

intermediate

What is the Authorization header value?

Given username 'user1' and password 'pass123', what is the correct Authorization header value in Basic Authentication?

Postman

import base64
credentials = 'user1:pass123'
encoded = base64.b64encode(credentials.encode()).decode()
print(f'Basic {encoded}')

A Basic dXNlcjE6cGFzczEyMw==

B Basic dXNlcjE6cGFzczEyMw

C Basic dXNlcjE7cGFzczEyMw==

D Basic dXNlcjE6cGFzczEyMw===

💡 Hint

Check the exact Base64 encoding of 'user1:pass123'.

The string 'user1:pass123' encoded in Base64 is 'dXNlcjE6cGFzczEyMw=='. The Authorization header must be 'Basic ' plus this string.

❓ locator

advanced

Identify the correct Postman setting for Basic Auth

Where in Postman do you set the username and password for Basic Authentication?

A Under the Authorization tab, select 'Basic Auth' and enter username and password fields

B In the Headers tab, manually add 'Authorization' header with encoded value

C In the Params tab, add username and password as query parameters

D In the Body tab, add username and password as form-data

💡 Hint

Postman has a dedicated place for authentication types.

Postman provides an Authorization tab where you can select Basic Auth and enter credentials. It automatically encodes and adds the header.

❓ assertion

advanced

Which test script assertion verifies Basic Auth success?

In Postman test scripts, which assertion correctly checks that the server accepted Basic Authentication by returning status 200?

Postman

pm.test('Basic Auth success', () => {
    pm.response.to.have.status(200);
});

A pm.test('Basic Auth success', () => { pm.response.to.have.status(500); });

B pm.test('Basic Auth success', () => { pm.response.to.have.status(401); });

C pm.test('Basic Auth success', () => { pm.response.to.have.status(200); });

D pm.test('Basic Auth success', () => { pm.response.to.have.status(404); });

💡 Hint

Success means HTTP 200 OK status.

A 200 status code means the server accepted the credentials and authorized the request.

🔧 Debug

expert

Why does this Postman Basic Auth test fail?

This Postman test script fails even though the username and password are correct. What is the likely cause? pm.test('Check Auth', () => { pm.response.to.have.status(200); pm.expect(pm.request.headers.get('Authorization')).to.eql('Basic dXNlcjE6cGFzczEyMw=='); });

A The Authorization header value is case sensitive and must be 'basic' lowercase

B The Authorization header is automatically removed by Postman before sending

C The Authorization header value includes 'Basic ' prefix, missing in the assertion

D The Authorization header value is dynamic and should be retrieved from pm.request.headers without hardcoding

💡 Hint

Check how the Authorization header is accessed and compared in the test.

The test compares the Authorization header to a hardcoded string. If credentials change or encoding differs, the test fails. It's better to dynamically check or decode the header.

Practice

1. What does Basic Authentication in Postman primarily require to access a protected API?

easy

A. A username and password

B. An API key only

C. A token generated by OAuth

D. No credentials, just the URL

Solution

1. Step 1: Understand Basic Authentication

   Basic Authentication requires a username and password to verify identity.

2. Step 2: Identify Postman's method

   Postman uses these credentials to add an Authorization header automatically.

3. Final Answer:

   A username and password -> Option A

4. Quick Check:

   Basic Auth = username + password [OK]

Hint: Basic Auth always needs username and password [OK]

Common Mistakes:

• Confusing Basic Auth with API key or OAuth tokens
• Thinking no credentials are needed
• Using only username or only password

2. Which is the correct way to set Basic Authentication in Postman?

easy

A. Select 'Basic Auth' in the Authorization tab and enter credentials

B. Use the Body tab to send username and password

C. Put credentials in the URL query parameters

D. Add username and password in the Headers tab manually

Solution

1. Step 1: Locate Authorization tab in Postman

   Postman provides an Authorization tab to set authentication types easily.

2. Step 2: Choose Basic Auth and enter credentials

   Selecting Basic Auth lets you enter username and password which Postman encodes automatically.

3. Final Answer:

   Select 'Basic Auth' in the Authorization tab and enter credentials -> Option A

4. Quick Check:

   Use Authorization tab for Basic Auth [OK]

Hint: Use Authorization tab, not Headers or Body [OK]

Common Mistakes:

• Manually adding Authorization header incorrectly
• Putting credentials in URL which is insecure
• Sending credentials in request body for Basic Auth

3. What will Postman send in the Authorization header when you enter username 'user1' and password 'pass123' for Basic Auth?

medium

A. Authorization: Basic user1:pass123

B. Authorization: Bearer user1:pass123

C. Authorization: Basic dXNlcjE6cGFzczEyMw==

D. Authorization: Token dXNlcjE6cGFzczEyMw==

Solution

1. Step 1: Understand Basic Auth header format

   Basic Auth sends 'Authorization: Basic ' plus base64 encoding of 'username:password'.

2. Step 2: Encode 'user1:pass123' in base64

   Encoding 'user1:pass123' results in 'dXNlcjE6cGFzczEyMw=='.

3. Final Answer:

   Authorization: Basic dXNlcjE6cGFzczEyMw== -> Option C

4. Quick Check:

   Basic Auth header = 'Basic ' + base64(username:password) [OK]

Hint: Basic Auth header is 'Basic ' + base64(username:password) [OK]

Common Mistakes:

• Using 'Bearer' instead of 'Basic'
• Sending plain username:password without encoding
• Confusing token or API key formats

4. You set Basic Auth in Postman but get a 401 Unauthorized error. What is the most likely cause?

medium

A. Using HTTPS instead of HTTP

B. Incorrect username or password entered

C. Headers tab is empty

D. Request body is missing

Solution

1. Step 1: Understand 401 Unauthorized meaning

   401 means the server rejected the credentials provided.

2. Step 2: Check credentials correctness

   Most common cause is wrong username or password causing authentication failure.

3. Final Answer:

   Incorrect username or password entered -> Option B

4. Quick Check:

   401 error = bad credentials [OK]

Hint: 401 usually means wrong username or password [OK]

Common Mistakes:

• Thinking HTTPS causes 401 error
• Assuming missing body causes authentication failure
• Ignoring credential typos

5. You want to test an API with Basic Auth but keep your password secure. Which Postman feature helps you avoid exposing your password in the request headers?

hard

A. Write the password directly in the URL

B. Disable SSL verification

C. Send credentials in the request body as plain text

D. Use environment variables to store credentials and reference them

Solution

1. Step 1: Identify secure ways to handle credentials

   Storing credentials in environment variables keeps them hidden and reusable.

2. Step 2: Use variables in Authorization tab

   Referencing variables in Basic Auth fields avoids hardcoding sensitive info in requests.

3. Final Answer:

   Use environment variables to store credentials and reference them -> Option D

4. Quick Check:

   Environment variables protect sensitive data [OK]

Hint: Use environment variables for credentials security [OK]

Common Mistakes:

• Putting password in URL exposes it
• Sending password in body is insecure for Basic Auth
• Disabling SSL reduces security, not protects password