Professional Guide to Load Testing with JMeter (With and Without Authentication)

What is Load Testing?

Load testing is a type of performance testing that simulates real-world traffic to a web application. It helps identify how a system behaves under expected user loads and helps uncover potential performance bottlenecks.

Apache JMeter is one of the most widely used tools for load testing. In this guide, we’ll cover step-by-step instructions on how to conduct load testing using JMeter for both authenticated and non-authenticated users.

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📦 Prerequisites

• Install Apache JMeter
• A running web application (we’ll use https://dummyapi.com)

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🔹 Test Scenario 1: Load Testing Without Authentication

Step 1: Create a Thread Group

1. Open JMeter
2. Right-click on Test Plan > Add > Threads (Users) > Thread Group
3. Configure:
   • Number of Threads (Users): 10 (increase gradually)
   • Ramp-Up Period: 5
   • Loop Count: 1

Step 2: Add HTTP Request

1. Right-click on Thread Group > Add > Sampler > HTTP Request
2. Configure:
   • Method: GET
   • Protocol: https
   • Server Name: dummyapi.com
   • Path: /public
   • Check: Use KeepAlive, Follow Redirects

Step 3: Add HTTP Header Manager (Optional)

1. Right-click on HTTP Request > Add > Config Element > HTTP Header Manager
2. Add:
   • Name: Content-Type, Value: application/json

Step 4: Add Listener

1. Right-click on Thread Group > Add > Listener > View Results Tree
2. Also add Summary Report for statistical output

Step 5: Run the Test

1. Click the Start button ▶️ on the toolbar
2. View Results in Tree and Summary Report

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🔒 Test Scenario 2: Load Testing With Authentication

Step 1: Login Request

1. Right-click on Thread Group > Add > Sampler > HTTP Request
2. Configure:
   • Method: POST
   • Protocol: https
   • Server Name: dummyapi.com
   • Path: /api/login/
   • Body Data:

{
  "username": "admin@dummy.com",
  "password": "12345678"
}

3. Add HTTP Header Manager with:
   • Content-Type: application/json

Step 2: Extract Auth Token (Using JSON Extractor)

1. Right-click on login HTTP request > Add > Post Processors > JSON Extractor
2. Add:
   • Name of Variable: access_token
   • JSON Path Expression: $.access

Step 3: Authenticated Request

1. Add another HTTP Request after login
2. Set:
   • Method: GET
   • Path: /user/dashboard/
3. Add HTTP Header Manager:
   • Authorization: Bearer ${access_token}
   • Content-Type: application/json

Step 4: Add Listener

• As before, add View Results Tree and Summary Report

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📊 Running the Load Test

• Gradually increase users: 10, 20, 30, … up to 100
• Monitor errors and latency
• Validate application performance under load

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✅ Tips for Real-World Testing

• Use realistic data sets with CSV Data Set Config
• Simulate think time with Timers
• Add assertions to validate correctness
• Run tests from CI pipelines (Jenkins or GitHub Actions)

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📈 Monitoring Performance

Integrate with Prometheus and Grafana for real-time server metrics like:

• CPU, Memory, Disk Usage
• Active Threads
• HTTP Response Times

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Conclusion: Load testing with JMeter is critical for understanding how your application behaves under stress. By testing both authenticated and non-authenticated flows, you ensure a reliable and scalable user experience.

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