Understanding TestNG Assertions

Introduction

Assertions in TestNG are a way to verify whether the expected result and the actual result match or not. An example of assertion can be logging into the website, checking the title of the webpage, verifying the functionality of an input box that takes only integers, etc.

We should remember that an assertion in TestNG is successful only if there are no exceptions thrown during the test case execution.

Syntax for TestNG Assertions

import org.testng.Assert;

public class AssertionExample {

    public void testStringEquality() {
        String actual = "Hello, TestNG";
        String expected = "Hello, TestNG";

        // Assertion using TestNG
        Assert.assertEquals(actual, expected, "String equality check failed");
    }
}

In this example, the assertEquals method is used to verify whether the actual string matches the expected string. If not, an error message ("String equality check failed") will be displayed.

How to Use Assertions in TestNG

import org.testng.Assert;

public class AssertionExample {

    public void testNumericInequality() {
        int actual = 10;
        int expected = 5;

        // Assertion using TestNG
        Assert.assertNotEquals(actual, expected, "Numeric inequality check failed");
    }
}

In this example, assertNotEquals is used to ensure that the actual numeric value is not equal to the expected value. If the assertion fails, the specified error message ("Numeric inequality check failed") will be displayed.

Using Messages as a Parameter in TestNG Asserts

Adding a custom message to assertions can significantly improve the clarity of test reports. Let's enhance our previous example:

import org.testng.Assert;

public class AssertionExample {

    public void testArrayEquality() {
        int[] actualArray = {1, 2, 3};
        int[] expectedArray = {1, 2, 3};

        // Assertion using TestNG with a custom message
        Assert.assertEquals(actualArray, expectedArray, "Array equality check failed");
    }
}

Types of Asserts in TestNG

1.Hard Assert

Hard Asserts stop the test execution when an assert statement fails, and subsequent assert statements are not validated. They are the default type of asserts in TestNG.

import org.testng.Assert;
import org.testng.annotations.Test;

public class HardAssertExample {

    @Test
    public void testLogin() {
        // Perform login
        boolean loginSuccessful = performLogin("username", "password");

        // Hard Assertion
        Assert.assertTrue(loginSuccessful, "Login failed");

        // Subsequent statements executed only if login is successful
        // Perform other actions after successful login
    }

    private boolean performLogin(String username, String password) {
        // Implementation of login logic
        // Return true if login is successful, false otherwise
        return true;
    }
}

2.Soft Assert

Soft Assert is the opposite of hard asserts, where the subsequent assertions keep on running even though one assert validation fails, i.e. the test execution does not stop. To use this, you need to include the package org.testng.asserts.SoftAssert.

import org.testng.asserts.SoftAssert;
import org.testng.annotations.Test;

public class SoftAssertExample {

    @Test
    public void testProductDetails() {
        SoftAssert softAssert = new SoftAssert();

        // Check product details
        softAssert.assertEquals(getProductName(), "Laptop", "Incorrect product name");
        softAssert.assertEquals(getProductPrice(), 1200, "Incorrect product price");
        softAssert.assertTrue(isProductInStock(), "Product out of stock");

        // Mark test as failed if any soft assertion fails
        softAssert.assertAll();
    }

    private String getProductName() {
        // Implementation to retrieve product name
        return "Laptop";
    }

    private int getProductPrice() {
        // Implementation to retrieve product price
        return 1200;
    }

    private boolean isProductInStock() {
        // Implementation to check if the product is in stock
        return true;
    }
}

Difference: Hard Asserts vs Soft Asserts

Commonly Used TestNG Assert Methods

//assertEquals: Verifies that two values are equal.
Assert.assertEquals(actual, expected, "Assertion Failure Message");

//assertNotEquals: Verifies that two values are not equal.
Assert.assertNotEquals(actual, expected, "Assertion Failure Message"); 

//assertTrue: Verifies that the provided condition is true.
Assert.assertTrue(condition, "Assertion Failure Message"); 

//assertFalse: Verifies that the provided condition is false.
Assert.assertFalse(condition, "Assertion Failure Message"); 

//assertNull: Verifies that the provided object reference is null.
Assert.assertNull(object, "Assertion Failure Message"); 

//assertNotNull: Verifies that the provided object reference is not null.
Assert.assertNotNull(object, "Assertion Failure Message"); 

//assertThrows: Verifies that a specific exception is thrown during the execution of a test.
Assert.assertThrows(Exception.class, () -> { 
    Code that should throw the specified exception
},"Assertion Failure Message");

Conclusion

In the realm of software testing, assertions are your trusty companions, aiding in the validation of expected outcomes. TestNG provides a robust set of assertion methods that cater to diverse testing scenarios. By incorporating these assertions into your test suites and adhering to best practices, you can enhance the reliability and effectiveness of your testing efforts. Embrace TestNG assertions, and empower your tests to unveil the true potential of your code. Happy testing! 🧪🚀