pages\BasePage.java

package pages;

import org.openqa.selenium.WebDriver;

public class BasePage {

    WebDriver driver;
    public final String BASE_URL = "https://www.saucedemo.com/";

    public BasePage(WebDriver driver) {
        this.driver = driver;
    }
}

pages\LoginPage.java

package pages;

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;

public class LoginPage extends BasePage{

    private final By USERNAME_FIELD = By.id("user-name");
    private final By PASSWORD_FIELD = By.id("password");
    private final By LOGIN_BUTTON = By.id("login-button");
    private final By ERROR_MESSAGE = By.cssSelector("[data-test=error]");

    public LoginPage(WebDriver driver) {
        super(driver);
    }

    public void open() {
        driver.get(BASE_URL);
    }

    public void login(String user, String password) {
        driver.findElement(USERNAME_FIELD).sendKeys(user);
        driver.findElement(PASSWORD_FIELD).sendKeys(password);
        driver.findElement(LOGIN_BUTTON).click();
    }

    public String getErrorMessage() {
        return driver.findElement(ERROR_MESSAGE).getText();
    }
}

pages\ProductsPage.java

package pages;

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;

public class ProductsPage extends BasePage{

    private final By TITLE = By.cssSelector("[data-test = title]");
    private final By CART = By.cssSelector("[data-test = shopping-cart-link]");
    private final String ADD_TO_CART_PATTERN =
            "//*[text()='%s']//ancestor::div[@class='inventory_item']//button[text()='Add to cart']";

    public ProductsPage(WebDriver driver) {
        super(driver);
    }

    public void open() {
        driver.get(BASE_URL + "/inventory.html");
    }

    public String getTitle() {
        return driver.findElement(TITLE).getText();
    }

    public void addToCart(String product) {
        driver.findElement(By.xpath(String.format(ADD_TO_CART_PATTERN, product))).click();
    }

    public void clickCart() {
        driver.findElement(CART).click();
    }
}

tests\BaseTest.java

package tests;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.chrome.ChromeOptions;
import org.testng.annotations.AfterMethod;
import org.testng.annotations.BeforeMethod;
import pages.LoginPage;
import pages.ProductsPage;

import java.time.Duration;
import java.util.HashMap;

public class BaseTest {

    WebDriver driver;
    LoginPage loginPage;
    ProductsPage productsPage;

    @BeforeMethod(alwaysRun = true)
    public void setUp() {
        ChromeOptions options = new ChromeOptions();
        HashMap<String, Object> chromePrefs = new HashMap<>();
        chromePrefs.put("credentials_enable_service", false);
        chromePrefs.put("profile.password_manager_enabled", false);
        options.setExperimentalOption("prefs", chromePrefs);
        options.addArguments("--incognito");
        options.addArguments("--disable-notifications");
        options.addArguments("--disable-popup-blocking");
        options.addArguments("--disable-infobars");
        driver = new ChromeDriver(options);

        driver.manage().window().maximize();
        driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(10));

        loginPage = new LoginPage(driver);
        productsPage = new ProductsPage(driver);
    }

    @AfterMethod(alwaysRun = true)
    public void tearDown() {
        if (driver != null) {
            driver.quit();
        }
    }
}

tests\CartTest.java

package tests;

import org.testng.annotations.Test;

public class CartTest extends BaseTest {

    String expectedProductName = "Sauce Labs Backpack";
    String expectedPriceOfProduct = "29.99";

    @Test
    public void checkCart() {
        //логинимся
        loginPage.open();
        loginPage.login("standard_user", "secret_sauce");

        //добавляем товары в корзину
        productsPage.addToCart("Sauce Labs Backpack");
        productsPage.addToCart("Test.allTheThings() T-Shirt (Red)");

        //нажимаем на кнопку корзина
        productsPage.clickCart();
    }
}

tests\LoginTest.java

package tests;

import org.testng.annotations.Test;

import static org.testng.Assert.assertEquals;

public class LoginTest extends BaseTest {

    @Test
    public void checkLoginWithPositiveCred() {
        loginPage.open();
        loginPage.login("standard_user", "secret_sauce");
        assertEquals(productsPage.getTitle(),
                "Products",
                "SO BAAAAAAD");
    }

    @Test
    public void chekLoginWithEmptyUserName() {
        loginPage.open();
        loginPage.login("", "secret_sauce");
        assertEquals(loginPage.getErrorMessage(),
                "Epic sadface: Username is required",
                "SO BAAAAAD");
    }

    @Test
    public void chekLoginWithEmptyPassword() {
        loginPage.open();
        loginPage.login("standard_user", "");
        assertEquals(loginPage.getErrorMessage(),
                "Epic sadface: Password is required",
                "SO BBAAAAD");
    }

    @Test
    public void chekLoginWithNegativeCred() {
        loginPage.open();
        loginPage.login("test", "test");
        assertEquals(loginPage.getErrorMessage(),
                "Epic sadface: Username and password do not match any user in this service",
                "SO BAAAAD");
    }
}