LoginTest.java

import org.openqa.selenium.By;
import org.testng.Assert;
import org.testng.annotations.Test;

public class LoginTest extends BaseTest {

    @Test
    public void checkLoginWithPositiveCred() {
        driver.get("https://www.saucedemo.com/");
        driver.findElement(By.id("user-name")).sendKeys("standard_user");
        driver.findElement(By.name("password")).sendKeys("secret_sauce");
        driver.findElement(By.className("submit-button")).click();
        String title = driver.findElement(By.cssSelector("[data-test = title]")).getText();
        Assert.assertEquals(title, "Products");
    }

    @Test
    public void chekLoginWithEmptyUserName() {
        driver.get("https://www.saucedemo.com/");
        driver.findElement(By.id("user-name")).sendKeys("");
        driver.findElement(By.name("password")).sendKeys("secret_sauce");
        driver.findElement(By.className("submit-button")).click();
        String error = driver.findElement(By.cssSelector("[data-test = error]")).getText();
        Assert.assertEquals(error, "Epic sadface: Username is required");
    }

    @Test
    public void chekLoginWithEmptyPassword() {
        driver.get("https://www.saucedemo.com/");
        driver.findElement(By.id("user-name")).sendKeys("standard_user");
        driver.findElement(By.name("password")).sendKeys("");
        driver.findElement(By.className("submit-button")).click();
        String error = driver.findElement(By.cssSelector("[data-test = error]")).getText();
        Assert.assertEquals(error, "Epic sadface: Password is required");

    }

    @Test
    public void chekLoginWithNegativeCred() {
        driver.get("https://www.saucedemo.com/");
        driver.findElement(By.id("user-name")).sendKeys("test");
        driver.findElement(By.name("password")).sendKeys("secret_sauce");
        driver.findElement(By.className("submit-button")).click();
        String error = driver.findElement(By.cssSelector("[data-test = error]")).getText();
        Assert.assertEquals(error, "Epic sadface: Username and password do not match any user in this service");
    }
}