Integrating Selenium with pytest and JUnit — Test Runners and Assertions

Writing Selenium code in a standalone script works for learning, but real automation projects need a test framework — a structured way to organise tests, run them selectively, report results, and manage setup and teardown. In Python, the standard choice is pytest. In Java, it is JUnit 5 (or TestNG). This lesson shows you how to integrate Selenium with both frameworks, turning standalone scripts into professional test suites with fixtures, assertions, and lifecycle management.

Selenium + pytest (Python) and Selenium + JUnit (Java) #

A test framework provides three critical capabilities: lifecycle hooks (setup/teardown), rich assertions, and test discovery and execution. Integrating Selenium with a framework transforms your automation from scripts into a maintainable test suite.

# ── Selenium + pytest ──
# File: tests/test_login.py

import pytest
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC


# ── Fixture: shared browser instance with automatic cleanup ──
@pytest.fixture
def browser():
    options = webdriver.ChromeOptions()
    options.add_argument("--headless=new")  # Run without visible browser
    driver = webdriver.Chrome(options=options)
    driver.implicitly_wait(5)

    yield driver  # Test runs here

    driver.quit()  # Cleanup — always runs, even if test fails


# ── Test: successful login ──
def test_login_with_valid_credentials(browser):
    browser.get("https://www.saucedemo.com")

    browser.find_element(By.ID, "user-name").send_keys("standard_user")
    browser.find_element(By.ID, "password").send_keys("secret_sauce")
    browser.find_element(By.ID, "login-button").click()

    WebDriverWait(browser, 10).until(
        EC.url_contains("inventory")
    )

    assert "inventory" in browser.current_url
    products = browser.find_elements(By.CLASS_NAME, "inventory_item")
    assert len(products) == 6, f"Expected 6 products, found {len(products)}"


# ── Test: login with wrong password ──
def test_login_with_invalid_password(browser):
    browser.get("https://www.saucedemo.com")

    browser.find_element(By.ID, "user-name").send_keys("standard_user")
    browser.find_element(By.ID, "password").send_keys("wrong_password")
    browser.find_element(By.ID, "login-button").click()

    error_msg = WebDriverWait(browser, 5).until(
        EC.presence_of_element_located((By.CSS_SELECTOR, "[data-test='error']"))
    )

    assert "do not match" in error_msg.text.lower()


# ── Test: login with empty fields ──
def test_login_with_empty_fields(browser):
    browser.get("https://www.saucedemo.com")

    browser.find_element(By.ID, "login-button").click()

    error_msg = WebDriverWait(browser, 5).until(
        EC.presence_of_element_located((By.CSS_SELECTOR, "[data-test='error']"))
    )

    assert "username is required" in error_msg.text.lower()


# Run with: pytest tests/test_login.py -v

// ── Selenium + JUnit 5 ──
// File: src/test/java/LoginTest.java

import org.junit.jupiter.api.*;
import org.openqa.selenium.*;
import org.openqa.selenium.chrome.*;
import org.openqa.selenium.support.ui.*;
import java.time.Duration;
import static org.junit.jupiter.api.Assertions.*;

class LoginTest {
    private WebDriver driver;
    private WebDriverWait wait;

    @BeforeEach
    void setUp() {
        ChromeOptions options = new ChromeOptions();
        options.addArguments("--headless=new");
        driver = new ChromeDriver(options);
        driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(5));
        wait = new WebDriverWait(driver, Duration.ofSeconds(10));
    }

    @AfterEach
    void tearDown() {
        if (driver != null) {
            driver.quit();
        }
    }

    @Test
    @DisplayName("Login with valid credentials shows inventory page")
    void testValidLogin() {
        driver.get("https://www.saucedemo.com");
        driver.findElement(By.id("user-name")).sendKeys("standard_user");
        driver.findElement(By.id("password")).sendKeys("secret_sauce");
        driver.findElement(By.id("login-button")).click();

        wait.until(ExpectedConditions.urlContains("inventory"));
        assertTrue(driver.getCurrentUrl().contains("inventory"));
    }
}

Common Mistakes #

Mistake 1 — Creating a new browser instance inside each test function #

❌ Wrong: Writing driver = webdriver.Chrome() at the start of every test function and driver.quit() at the end, duplicating setup code across 50 tests.

✅ Correct: Creating a shared pytest fixture (or JUnit @BeforeEach) that handles browser creation and cleanup in one place. Every test simply requests the fixture.

Mistake 2 — Not running tests in headless mode during CI #

❌ Wrong: Tests that open visible browser windows fail in CI/CD pipelines because there is no display server.

✅ Correct: Configuring headless mode via ChromeOptions when running in CI, while allowing headed mode during local development for visual debugging.