Learn How to Use Postman for API Testing: A Step-by-Step Manual

Here's your complete beginner-friendly step-by-step guide to using Postman for the Express.js project we built in Day 11 (Student API).

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🎯 Goal

You will learn how to use Postman to test these API routes:

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🧰 What You Need

✅ Your Express server running on http://localhost:5000
✅ Postman installed

👉 Download Postman and install it (if not already)

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🧪 Step-by-Step: Testing with Postman

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✅ Step 1: Open Postman

• After opening Postman, click on "New" → "HTTP Request"

• A tab will open to create your first API request

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✅ Step 2: Test GET Request

Goal: Fetch all students from your API

1. Select method: GET

2. URL:

    http://localhost:5000/students
   

3. Click Send

📥 You will get a response like:

[
  { "id": 1, "name": "Payal" },
  { "id": 2, "name": "Amit" }
]

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✅ Step 3: Test POST Request

Goal: Add a new student

1. Select method: POST

2. URL:

    http://localhost:5000/students
   

3. Click on Body tab

4. Select raw

5. From dropdown on right, choose JSON

6. Paste this JSON:

{
  "name": "Ravi"
}

7. Click Send

📤 You’ll get a response like:

{ "id": 3, "name": "Ravi" }

✅ Also, now GET request will include Ravi!

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✅ Step 4: Test PUT Request (Update Student)

Goal: Update a student’s name

1. Select method: PUT

2. URL (use a real ID, example 2):

    http://localhost:5000/students/2
   

3. Go to Body → raw → JSON

4. Paste:

{
  "name": "Updated Amit"
}

5. Click Send

📤 Response:

{ "id": 2, "name": "Updated Amit" }

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✅ Step 5: Test DELETE Request

Goal: Delete a student

1. Select method: DELETE

2. URL (use the ID you want to delete, like 3):

    http://localhost:5000/students/3
   

3. Click Send

📤 Response:

{ "message": "Student deleted successfully" }

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👀 Tips for Beginners

• Always use GET from the browser, but for POST, PUT, and DELETE, Postman is the best tool

• If you get Cannot GET /students, check if your server is running

• Restart server if you change index.js

• If Postman hangs, check port, check firewall, or restart app

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💡 Bonus: Save Requests as a Collection

1. Click Save near Send button

2. Create a Collection called Student API

3. Save all requests (GET, POST, PUT, DELETE) inside it
   ✅ Now you can access them anytime without rewriting.

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✅ Summary

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