REST API fundamentals review in Postman - Test Execution Trace

Test Overview

This test sends a GET request to a REST API endpoint to retrieve user data. It verifies that the response status is 200 OK and that the response body contains the expected user ID and name.

Test Code - Postman

Postman

pm.test("Status code is 200", function () {
    pm.response.to.have.status(200);
});

pm.test("Response has correct user data", function () {
    const jsonData = pm.response.json();
    pm.expect(jsonData.id).to.eql(1);
    pm.expect(jsonData.name).to.eql("John Doe");
});

Execution Trace - 4 Steps

Step	Action	System State	Assertion	Result
1	Send GET request to https://api.example.com/users/1	Postman sends HTTP GET request to the API endpoint	—	PASS
2	Receive HTTP response from the server	Response received with status code 200 and JSON body {"id":1,"name":"John Doe"}	—	PASS
3	Check that response status code is 200	Response status code is 200 OK	pm.response.to.have.status(200)	PASS
4	Parse response JSON and verify user id and name	Response JSON parsed as {id:1, name:"John Doe"}	pm.expect(jsonData.id).to.eql(1) and pm.expect(jsonData.name).to.eql("John Doe")	PASS

Failure Scenario

Failing Condition: Response status code is not 200 or user data does not match expected values

Execution Trace Quiz - 3 Questions

What does the test verify first after sending the GET request?

A That the response status code is 200

B That the response body contains a list of users

C That the request method is POST

D That the response time is less than 1 second

Key Result

Always verify both the HTTP status code and the response body content to ensure the API behaves as expected.

Practice

1. Which HTTP method is typically used to retrieve data from a REST API without changing it?

easy

A. POST

B. GET

C. PUT

D. DELETE

Solution

1. Step 1: Understand HTTP methods

   GET is used to request data without modifying it, while POST, PUT, DELETE change data.

2. Step 2: Identify method for data retrieval

   Since we want to retrieve data without changes, GET is the correct method.

3. Final Answer:

   GET -> Option B

4. Quick Check:

   Retrieve data = GET [OK]

Hint: GET is for reading data, others modify it [OK]

Common Mistakes:

• Confusing POST with GET for data retrieval
• Using DELETE to get data
• Thinking PUT retrieves data

2. Which of the following is the correct way to set the HTTP method to POST in Postman?

easy

A. Add 'method: POST' in the Headers tab

B. Type 'POST' in the URL field

C. Select POST from the dropdown next to the URL input

D. Use the Body tab to set method to POST

Solution

1. Step 1: Locate HTTP method selector in Postman

   Postman has a dropdown menu next to the URL field to choose HTTP methods.

2. Step 2: Confirm correct method selection

   Selecting POST from this dropdown sets the request method properly.

3. Final Answer:

   Select POST from the dropdown next to the URL input -> Option C

4. Quick Check:

   Method dropdown sets HTTP method [OK]

Hint: Use dropdown near URL to pick method [OK]

Common Mistakes:

• Typing method name in URL field
• Trying to set method in Headers
• Confusing Body tab with method setting

3. What will be the status code returned by a successful DELETE request in a REST API?

medium

A. 404 Not Found

B. 201 Created

C. 200 OK

D. 204 No Content

Solution

1. Step 1: Understand DELETE success responses

   A successful DELETE often returns 204 No Content, meaning the resource was deleted and no content is returned.

2. Step 2: Compare other status codes

   200 OK means success with content, 201 Created is for new resource creation, 404 Not Found means resource missing.

3. Final Answer:

   204 No Content -> Option D

4. Quick Check:

   DELETE success = 204 No Content [OK]

Hint: DELETE success usually returns 204 No Content [OK]

Common Mistakes:

• Choosing 201 Created for DELETE
• Assuming 200 OK always returns content
• Confusing 404 with success

4. You send a POST request in Postman but get a 405 Method Not Allowed error. What is the most likely cause?

medium

A. The API endpoint does not support POST method

B. The URL is incorrect

C. The request body is empty

D. The server is down

Solution

1. Step 1: Understand 405 error meaning

   405 Method Not Allowed means the server recognizes the URL but the HTTP method used is not supported on that endpoint.

2. Step 2: Eliminate other options

   Incorrect URL usually gives 404, empty body usually does not cause 405, server down causes no response or 5xx errors.

3. Final Answer:

   The API endpoint does not support POST method -> Option A

4. Quick Check:

   405 = Method not allowed on endpoint [OK]

Hint: 405 means method not allowed on URL [OK]

Common Mistakes:

• Confusing 405 with 404 Not Found
• Assuming empty body causes 405
• Thinking server down causes 405

5. You want to test a REST API endpoint that updates user data. Which combination of HTTP method and Postman feature is best to use?

hard

A. PUT method with Body tab to send JSON data

B. GET method with Params tab to send JSON data

C. DELETE method with Headers tab to send JSON data

D. POST method with URL query parameters

Solution

1. Step 1: Identify method for updating data

   PUT is the standard HTTP method to update existing data in REST APIs.

2. Step 2: Choose Postman feature to send data

   The Body tab allows sending JSON data payload, which is needed to update user data.

3. Step 3: Evaluate other options

   GET does not update data, DELETE removes data, and URL query parameters are not suitable for sending JSON update data.

4. Final Answer:

   PUT method with Body tab to send JSON data -> Option A

5. Quick Check:

   Update data = PUT + Body JSON [OK]

Hint: Use PUT with Body for updates in Postman [OK]

Common Mistakes:

• Using GET to update data
• Sending JSON in URL parameters
• Confusing DELETE with update