SSL certificate validation in Postman - Build an Automation Script

Validate SSL certificate for API endpoint in Postman

Preconditions (3)

Step 1: Open Postman and create a new GET request

Step 2: Enter the HTTPS API endpoint URL (e.g., https://api.example.com/data)

Step 3: Send the request

Step 4: Observe the response status and body

Step 5: Disable SSL certificate validation in Postman settings

Step 6: Send the same request again

Step 7: Observe the response status and body

✅ Expected Result: When SSL certificate validation is enabled, the request should succeed only if the SSL certificate is valid. When disabled, the request should succeed even if the certificate is invalid or self-signed.

Automation Requirements - Postman test scripts

Assertions Needed:

Verify response status code is 200 when SSL validation is enabled and certificate is valid

Verify error or failure occurs when SSL validation is enabled and certificate is invalid

Verify response status code is 200 when SSL validation is disabled regardless of certificate validity

Best Practices:

Use Postman environment variables for endpoint URLs

Use pm.test and pm.response assertions for validation

Do not disable SSL validation in production tests

Log clear messages for pass/fail results

Automated Solution

Postman

/* Postman test script to validate SSL certificate behavior */

pm.test('Response status is 200', function () {
    pm.response.to.have.status(200);
});

pm.test('Response time is less than 2000ms', function () {
    pm.expect(pm.response.responseTime).to.be.below(2000);
});

// Additional checks can be added based on response body or headers

// Note: SSL validation is controlled in Postman settings, not via script
// This script assumes SSL validation is enabled in settings

This Postman test script checks that the response status code is 200, indicating a successful HTTPS request with a valid SSL certificate.

Since SSL certificate validation is controlled by Postman settings, the script itself cannot enable or disable it. Instead, the tester must toggle SSL validation in Postman settings and observe the test results.

The test also checks that the response time is reasonable, which helps ensure the request completed properly.

Assertions use pm.test and pm.response to verify the response status and timing.

Common Mistakes - 3 Pitfalls

Trying to disable SSL validation via test scripts

Not verifying response status code

Using HTTP instead of HTTPS endpoint

Bonus Challenge

Now add data-driven testing with 3 different HTTPS endpoints: one with a valid SSL certificate, one with a self-signed certificate, and one with an expired certificate.

Show Hint

Practice

1. What does enabling SSL certificate validation in Postman do?

easy

A. It ensures Postman verifies the server's SSL certificate for secure connections.

B. It disables all SSL checks to speed up requests.

C. It automatically fixes invalid SSL certificates.

D. It encrypts the request body before sending.

Solution

1. Step 1: Understand SSL certificate validation purpose

   SSL certificate validation checks if the server's certificate is valid and trusted to secure data.

2. Step 2: Relate to Postman setting

   Enabling this setting makes Postman verify the SSL certificate before sending requests.

3. Final Answer:

   It ensures Postman verifies the server's SSL certificate for secure connections. -> Option A

4. Quick Check:

   SSL validation = verify server certificate [OK]

Hint: SSL validation means checking server certificates [OK]

Common Mistakes:

• Thinking SSL validation disables checks
• Believing it fixes certificates automatically
• Confusing encryption with validation

2. Which Postman setting controls SSL certificate validation?

easy

A. Enable Proxy in Settings > Proxy

B. Disable SSL verification toggle in Settings > General

C. Turn on Interceptor in Settings > Proxy

D. Set Environment variable SSL_VALIDATE

Solution

1. Step 1: Locate SSL validation setting in Postman

   Postman has a toggle named 'Disable SSL verification' under Settings > General.

2. Step 2: Understand toggle effect

   Turning this toggle ON disables SSL validation; turning it OFF enables validation.

3. Final Answer:

   Disable SSL verification toggle in Settings > General -> Option B

4. Quick Check:

   SSL toggle = Disable SSL verification [OK]

Hint: Look for 'Disable SSL verification' in General settings [OK]

Common Mistakes:

• Confusing proxy settings with SSL validation
• Thinking Interceptor controls SSL validation
• Assuming environment variables control SSL validation

3. What will happen if you send a request in Postman with SSL validation OFF to a server with an expired SSL certificate?

medium

A. Postman will block the request and show an SSL error.

B. Postman will automatically renew the server's certificate.

C. Postman will encrypt the request twice.

D. Postman will send the request ignoring the expired certificate.

Solution

1. Step 1: Understand SSL validation OFF effect

   When SSL validation is OFF, Postman does not check the server's certificate validity.

2. Step 2: Predict behavior with expired certificate

   Postman will ignore the expired certificate and send the request without error.

3. Final Answer:

   Postman will send the request ignoring the expired certificate. -> Option D

4. Quick Check:

   SSL off = ignore certificate errors [OK]

Hint: SSL off means ignore certificate problems [OK]

Common Mistakes:

• Assuming Postman blocks requests with SSL off
• Thinking Postman renews certificates
• Confusing encryption with validation

4. You enabled SSL certificate validation in Postman but still receive SSL errors for a trusted server. What is the likely cause?

medium

A. The server's SSL certificate is self-signed or not trusted by your system.

B. Postman does not support SSL validation for HTTPS.

C. You forgot to enable proxy settings in Postman.

D. Your internet connection is offline.

Solution

1. Step 1: Analyze SSL error despite validation enabled

   If SSL validation is ON but errors appear, the certificate might be self-signed or untrusted.

2. Step 2: Exclude other causes

   Postman supports SSL validation; proxy or internet issues cause different errors.

3. Final Answer:

   The server's SSL certificate is self-signed or not trusted by your system. -> Option A

4. Quick Check:

   SSL errors usually mean untrusted certificate [OK]

Hint: Untrusted certs cause SSL errors even if validation is ON [OK]

Common Mistakes:

• Thinking Postman lacks SSL validation support
• Blaming proxy settings for SSL errors
• Assuming offline connection causes SSL errors

5. You want to test an API with a self-signed SSL certificate in Postman without errors. What is the best approach?

hard

A. Use a different tool that ignores SSL by default.

B. Turn OFF SSL certificate validation in Postman settings temporarily.

C. Import the self-signed certificate into your system's trusted store and keep validation ON.

D. Send requests only over HTTP instead of HTTPS.

Solution

1. Step 1: Understand testing with self-signed certificates

   Self-signed certificates cause SSL errors unless trusted by the system.

2. Step 2: Choose best practice for secure testing

   Importing the certificate into the trusted store allows validation ON without errors, ensuring real security testing.

3. Step 3: Evaluate other options

   Turning off validation skips security checks; using HTTP or other tools reduces test accuracy.

4. Final Answer:

   Import the self-signed certificate into your system's trusted store and keep validation ON. -> Option C

5. Quick Check:

   Trust certs to keep SSL validation ON [OK]

Hint: Trust self-signed certs to keep SSL validation ON [OK]

Common Mistakes:

• Disabling SSL validation permanently
• Ignoring security by using HTTP
• Switching tools instead of fixing trust