API Performance Testing with Gatling (Java)

Why Choose Gatling over Other Performance Testing Tools?

When selecting a performance testing tool, it's important to evaluate the strengths and limitations of each. Below is a comparison of Gatling with other popular tools like JMeter and LoadRunner, focusing on CI/CD integration, maintainability, cost, and results management.

🔹 Apache JMeter

Pros: Intuitive UI: Easy to use, even without referencing documentation. Good for quick manual test setups and exploratory performance testing.

Cons: Limited CI/CD Integration: Cannot be easily run as part of a build pipeline for faster feedback. Script Maintenance: Scripts require careful version control and are harder to manage in a collaborative environment. Results Management: Lacks built-in support for historical result archiving or dashboarding.

🔹 LoadRunner Pros: Enterprise-grade tool with robust test execution and reporting. Historical results available through Performance Center. Cons: Cost: Licensed tool with significant cost implications. Execution Dependency: Requires Performance Center Scheduler to run tests. Complexity: Requires coding skills to create and maintain scripts.

🔹 Gatling Pros: CI/CD Friendly: Seamlessly integrates with Jenkins and other pipelines. Script Management: Gatling scripts are written in code (Scala/Java/Kotlin) and can be version-controlled in Git (e.g., Bitbucket). Result Reporting: Test results can be uploaded to S3 Buckets. HTML reports are automatically generated and accessible from Jenkins builds. Lightweight and fast execution. Cons: Requires some coding knowledge (supports multiple languages like Java, Scala, kotlin etc), but offers greater flexibility and reusability in return.

This project demonstrates API performance testing using Gatling with Java. It includes sample simulations for REST API endpoints.

Project Structure

• src/test/java/common/ProjectInfo.java: Configuration constants (base URL, user count, etc.)
• src/test/java/simulations/LoadSimulation.java: Main Gatling simulation scenario.

Prerequisites

• Java 21 or higher
• Maven 3.x

How to Run

1. Clone the repository.
2. Navigate to the project directory.
3. Run the Gatling simulation using Maven cmd

   mvn gatling:test
   

4. After execution, reports will be available in target/gatling directory.

Configuration

You can update test parameters in common/ProjectInfo.java:

• BASE_URL: API base URL
• USER_COUNT: Number of virtual users
• RAMP_DURATION: Ramp-up duration (seconds)
• TEST_DURATION: Total test duration (seconds)

Dependencies

• Gatling Java API
• JUnit (for test scope)

To add new API for Performance test

To add a new API endpoint for performance testing:

1. Create a Simulation Class

   • In src/test/java/simulations/, create a new Java class (e.g., NewApiSimulation.java).
   • Extend Simulation and define your scenario using Gatling's Java DSL.

2. Configure the Scenario

   • Set up HTTP requests, checks, and user injection profiles in your new simulation class.
   • Use configuration constants from common/ProjectInfo.java as needed.

3. Register the Simulation

   • By default, Gatling will discover all simulation classes in the test sources.
   • To run a specific simulation, use:

     mvn gatling:test -Dgatling.simulationClass=simulations.NewApiSimulation
     

Main Execution Flow at Runtime

1. Initialization

   • Gatling loads configuration from ProjectInfo.java and simulation classes.

2. Simulation Execution

   • The selected simulation defines:
     • HTTP protocol configuration (base URL, headers)
     • Scenario steps (requests, pauses, checks)
     • User injection profile (number of users, ramp-up, duration)

3. Test Run

   • Gatling injects virtual users and executes the scenario as defined.
   • Results (response times, success/failure, etc.) are collected.

4. Reporting

   • After execution, HTML reports are generated in target/gatling.
   • Sample report uploaded to target/gatling/loadsimulation-20250529083649185/index.html