Master JMeter: Step‑by‑Step Guide to Automate Weather API Load Testing

JMeter Introduction

JMeter is an open‑source, Java‑based testing tool used for functional and performance (stress/load) testing, especially effective for testing RESTful APIs.

How to Learn JMeter

To use JMeter for web functional or performance testing, you need a solid understanding of the HTTP protocol; otherwise many JMeter concepts will be hard to grasp.

Download and Run JMeter

Official website: http://jmeter.apache.org/

After extracting the archive, run bin/jmeter.bat. JMeter supports Chinese; select the language via Options → Choose Language.

Practical Example: Weather API

Goal: Retrieve weather data for a city.

Step 1: Send a request to obtain the city code, e.g. http://toy1.weather.com.cn/search?cityname=上海. The response contains the city code such as 101020100.

Step 2: Use the city code to request weather data, e.g. http://www.weather.com.cn/weather2d/101020100.html.

Step 1 – Create a Thread Group

All JMeter tasks must be placed under a Thread Group.

Step 2 – Add an HTTP Request

Configure a GET request to http://toy1.weather.com.cn/search?cityname=上海 as shown in the screenshot.

Step 3 – Add HTTP Header Manager

Select the HTTP Request, right‑click, Add → Config Element → HTTP Header Manager, then add the required header.

Step 4 – Add View Results Tree Listener

This listener shows the execution results.

Step 5 – Run Test and View Results

At this point the test runs successfully.

Step 6 – Add Assertion and Assertion Results

Right‑click the HTTP Request, Add → Assertions → Response Assertion, then define patterns to test. Add an Assertion Results listener to view failures.

Step 7 – Use User Defined Variables

Define a variable (e.g., city) via Thread Group → Add → Config Element → User Defined Variables, then reference it as ${city} in the HTTP Request.

Step 8 – Correlation (Extracting Data)

Use a Regular Expression Extractor on the first HTTP Request to capture the city code into a variable (e.g., ${citycode}), then use that variable in a second request: http://www.weather.com.cn/weather2d/${citycode}.html.

With the script complete, run it to see the final results.