How to write Performance test using JMeter

Writing performance tests with JMeter involves several steps. Here's a step-by-step guide to help you create a basic performance test using JMeter:

### Step 1: Install JMeter

If you haven't installed JMeter yet, you can download it from the official Apache JMeter website: https://jmeter.apache.org/download_jmeter.cgi

### Step 2: Create a Test Plan

1. **Launch JMeter:** Start JMeter by running the `jmeter.bat` (Windows) or `jmeter.sh` (Unix) file from the bin directory.

2. **Create a Test Plan:** In JMeter, a test plan is a container for your test. Right-click on the Test Plan in the left panel, select "Add" -> "Threads (Users)" -> "Thread Group." Configure the number of threads (simulated users), ramp-up time, and loop count according to your test scenario.

### Step 3: Add Sampler(s)

Samplers are the types of requests you want to send to your server. Common types include HTTP requests, FTP requests, and more.

1. **Add HTTP Request:** Right-click on the Thread Group, select "Add" -> "Sampler" -> "HTTP Request." Configure the server name or IP, path, and other necessary parameters.

### Step 4: Add Listeners

Listeners are used to view the results of your test. There are various types of listeners available in JMeter.

1. **Add Summary Report:** Right-click on the Thread Group, select "Add" -> "Listener" -> "Summary Report." This provides a summary of the test results.

2. **Add View Results Tree:** Right-click on the Thread Group, select "Add" -> "Listener" -> "View Results Tree." This listener shows detailed information about each request and response.

### Step 5: Configure Assertions (Optional)

Assertions are used to set criteria for the response. For example, you can add a Response Assertion to check if the response contains specific text.

1. **Add Response Assertion:** Right-click on the HTTP Request, select "Add" -> "Assertions" -> "Response Assertion." Configure the assertion according to your requirements.

### Step 6: Run the Test

1. **Configure Test Plan:** Set the necessary configurations in the Test Plan, such as the number of threads, ramp-up time, and loop count.

2. **Start the Test:** Click on the "Play" button or select "Run" -> "Start" from the menu bar to start the test. JMeter will start sending requests to the server according to your configuration.

3. **View Results:** Once the test is complete, you can view the results in the listeners you added. Analyze the results to identify any performance issues.

### Additional Tips:

- **Parameterization:** If you want to use different data for your requests, you can use CSV Data Set Config or other parameterization methods.

- **Correlation:** If your application uses dynamic values (like session IDs), you might need to extract and correlate these values between requests.

- **Distributed Testing:** For larger tests, you can set up JMeter in a distributed environment to distribute the load among multiple machines.

Remember to continuously monitor your server resources during the test to ensure your JMeter machine's limitations are not affecting the results.