Unable to call method which performing mouse actions to TestNG test case using selenium Java

Main Block:

    public class test3 extends utility {
        public WebDriver driver;
        @BeforeTest
        public void invokeBrowser() throws IOException {
            driver = base();
            driver.get(resource.getProperty("url"));
    
        }
    
        @Test
        public class thirdPage {
            public void main() {
    
                actionTest test3 = new actionTest();
                test3.executeTest();
            }
        }
    
    }

Code performing mouse Actions:

public class actionTest {   
    
    public void executeTest() {
    Actions execute = new Actions();    
    execute.moveToElement(driver.findElement(By.id("header-search-input"))).click().keyDown(Keys.SHIFT).sendKeys("Cricket").build().perform();
    driver.findElement(By.id("header-desktop-search-button")).click();
    }
    
    

}

Above code results in "NullPointerException" stating driver = null while executing block test3.executeTest();