Singleton in Selenium Framework

💡 What Is Singleton?

The Singleton Design Pattern means creating only one object (instance) of a class and reusing it wherever needed.

In Selenium automation, we use Singleton to make sure that only one WebDriver instance is created and used throughout the test execution.

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⚙️ Why We Need Singleton in Selenium

If we create multiple WebDriver instances in the same test run:

• 🪟 Multiple browser windows may open unnecessarily

• 🔄 Browser sessions may conflict

• ⚠️ Tests may fail or behave unexpectedly

👉 The Singleton pattern prevents this by allowing only one WebDriver instance to exist at a time.

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🧩 How Singleton Works

1️⃣ The constructor is private, so no one can create objects directly.
2️⃣ A static method provides access to the single instance.
3️⃣ The same instance is reused wherever it’s needed.

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🧱 Example: Singleton WebDriver Manager

package driver;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;

public class DriverSingleton {

    // Step 1: Create a private static instance variable
    private static WebDriver driver;

    // Step 2: Make the constructor private
    private DriverSingleton() { }

    // Step 3: Provide a public static method to get the driver instance
    public static WebDriver getDriver() {
        if (driver == null) {
            driver = new ChromeDriver();
            driver.manage().window().maximize();
        }
        return driver;
    }

    // Step 4: Quit the driver and reset it to null
    public static void quitDriver() {
        if (driver != null) {
            driver.quit();
            driver = null;
        }
    }
}

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✅ How to Use It

public class TestExample {
    public static void main(String[] args) {
        // Get the same WebDriver instance
        WebDriver driver = DriverSingleton.getDriver();

        driver.get("https://example.com");
        System.out.println(driver.getTitle());

        // Close the browser
        DriverSingleton.quitDriver();
    }
}

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🚀 Benefits of Using Singleton

✅ Only one browser instance per test run
✅ Easy to manage WebDriver lifecycle
✅ Saves memory and resources
✅ Reduces code duplication

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⚠️ Limitations

❌ Not suitable for parallel testing (multiple threads need separate driver instances)

👉 In that case, use ThreadLocal for thread safety — You can refer below link to the detailed explanation here: https://softwaretestingbugblab.blogspot.com/2025/10/ensuring-thread-safety-in-parallel-test.html

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🧾 In Short:

The Singleton Design Pattern in Selenium ensures that only one WebDriver instance is created and reused across the entire test execution — making your framework cleaner, efficient, and easy to maintain.