Scenario/Test steps:
1. Open a browser and navigate to TestURL
2. Scroll down some pixel and scroll up
For Scroll down:
WebDriver driver = new FirefoxDriver();
JavascriptExecutor jse = (JavascriptExecutor)driver;
jse.executeScript("window.scrollBy(0,250)");
OR, you can do as follows:
jse.executeScript("scroll(0, 250);");