Mastering Assertions in Selenium: A Comprehensive Guide

 Assertions in Selenium: A Comprehensive Guide

In Selenium, assertions are used to verify whether a certain condition is true or false during the execution of a test. If the condition is true, the test continues, but if it’s false, the test will fail, and the execution will stop. Assertions are useful to validate the expected behaviour of a web application.

v  There are two types of assertions commonly used in Selenium:

1. Hard Assertions (Built-in assert statements):
• These assertions immediately stop the test execution if the condition fails.
• If the assertion fails, an exception is thrown, and the subsequent steps are not executed.
• Hard assertions are typically used to check if specific conditions (e.g., page title, element visibility) are met.
2. Soft Assertions (from TestNG or JUnit):
• These allow the test to continue even if an assertion fails. All soft assertions are collected and reported at the end of the test execution.
• Soft assertions are helpful when you want to collect multiple validation results in a single run.

Using Hard Assertions in Selenium

Here is an example using JUnit (common assertion approach in Java for Selenium):

1. Hard Assertion Example with JUnit:

java

import org.junit.Assert;

import org.openqa.selenium.By;

import org.openqa.selenium.WebDriver;

import org.openqa.selenium.chrome.ChromeDriver;

 

public class HardAssertionExample {

    public static void main(String[] args) {

        WebDriver driver = new ChromeDriver();

        driver.get("http://example.com");

        // Hard assertion: Check if the page title is correct

        String expectedTitle = "Example Domain";

        String actualTitle = driver.getTitle();

       

        // This will throw an AssertionError if the titles don't match

        Assert.assertEquals(expectedTitle, actualTitle);

 

        // More steps will not be executed if the assertion fails

        driver.quit();

    }

}

Explanation:

• The assertEquals assertion checks if the actual page title matches the expected title.
• If the assertion fails, it throws an error and stops further test execution.

Using Soft Assertions in Selenium (TestNG Example)

In TestNG, you can use soft assertions. These allow tests to continue running even if an assertion fails.

2. Soft Assertion Example with TestNG:

java

import org.openqa.selenium.By;

import org.openqa.selenium.WebDriver;

import org.openqa.selenium.chrome.ChromeDriver;

import org.testng.asserts.SoftAssert;

 

public class SoftAssertionExample {

    public static void main(String[] args) {

        WebDriver driver = new ChromeDriver();

        driver.get("http://example.com");

 

        SoftAssert softAssert = new SoftAssert();

 

        // Soft assertion: Check if the page title is correct

        String expectedTitle = "Example Domain";

        String actualTitle = driver.getTitle();

 

        // This will not stop the test execution if it fails

        softAssert.assertEquals(actualTitle, expectedTitle);

 

        // You can perform more actions even if the assertion fails

        softAssert.assertTrue(driver.findElement(By.id("someElement")).isDisplayed());

 

        // Assert all at the end of the test

        softAssert.assertAll();

 

        driver.quit();

    }

}

Explanation:

• SoftAssert allows assertions to be executed even if the condition fails.
• The assertAll() method is called at the end to gather all assertion results and determine whether the test passed or failed.
• If any assertion fails, it will be reported, but the test will continue to execute the remaining steps.

v  Common Assertion Methods in Selenium (Using JUnit and TestNG)

      1. JUnit Assertions (Hard Assertions):

• assertTrue(condition): Verifies if the condition is true.
• assertFalse(condition): Verifies if the condition is false.
• assertEquals(expected, actual): Verifies if the expected value matches the actual value.
• assertNotEquals(expected, actual): Verifies if the expected value does not match the actual value.
• assertNull(object): Verifies if the object is null.
• assertNotNull(object): Verifies if the object is not null.

      2. TestNG Soft Assertions:

• assertTrue(condition): Verifies if the condition is true.
• assertFalse(condition): Verifies if the condition is false.
• assertEquals(expected, actual): Verifies if the expected value matches the actual value.
• assertNotEquals(expected, actual): Verifies if the expected value does not match the actual value.
• assertNull(object): Verifies if the object is null.
• assertNotNull(object): Verifies if the object is not null.

v  When to Use Assertions in Selenium:

• Validation: To validate the page title, element visibility, or other attributes during the test.
• Form Validation: To confirm that the correct data appears after form submission.
• Error Checking: To ensure that error messages, if any, are correctly displayed.
• State Validation: To check if specific elements are enabled, disabled, selected, or deselected.

In conclusion, assertions are an essential part of test automation in Selenium. You can use hard assertions for strict validation and soft assertions when you want to continue executing the test even after a failure.