Understanding JUnit assertions for Selenium Testing with Examples

Assert means “to state a fact or belief confidently” as per the English dictionary. In STLC (Software Test Life Cycle), if we want to test a use case, we follow the predefined steps mentioned in the respective user story. Then we compare the actual result with the expected result and drive to a conclusion about whether the test case passed or failed.

• Similarly, in Selenium, if we want to automate a test case and validate the output, we should use assert and verify whether the result is pass/fail/skip. 
• If we just keep writing the automation test cases and do not assert it properly, automation is of no use. 

Basically, the process of comparing the actual and expected result is called “Assert” in testing terminology. Going ahead, we’ll learn how to use different types of JUnit Assertions for Selenium Tests using examples in this guide. 

How to Assert in Selenium?

Selenium does not provide any assert feature; we need to use either JUnit or TestNG to assert test cases. JUnit and TestNG are the two popular Java testing frameworks which are open source and can be easily integrated with Selenium.

Unit testing means testing a single module in isolation and verifying it’s working as expected.

JUnit framework is widely used by developers to unit test small chunks/modules of newly created code before integrating it with the working code. Apart from developers, it is also used by testers to assert the tests in an automation framework.

Different types of Asserts

Hard Assert

In hard assert, the program execution stops as soon as an exception occurs and thereby skipping all the next steps in the test method. It throws an Assertion error and marks the test case as failed though all the steps in the test method were not executed. After the assert fails, the current test is skipped and the next @Test is executed.

Soft Assert

In some cases, we need the test execution to continue even when there is any exception encountered. Soft Asserts do not throw an Assertion error if there is any exception and rather record the failure. Later, it collects all the assertions throughout the @Test method and throws all the exceptions caught during the process with the assertAll() method.

Going ahead In this article, we are going to focus on integrating JUnit5 Testing framework with the Selenium project.

Benefits of JUnit5 over JUnit4

• JUnit5 comprises JUnit Platform, JUnit Jupiter and JUnit Vintage components.
• JUnit5 requires Java version 8 or above thereby supporting lambda functions which is a powerful feature in Java 8 and it was unavailable in JUnit4 as it works on the highest Java version as 7.
• JUnit 5 assertions methods have overloaded methods to support parsing error messages to be printed in case test fails
• Annotations have been refined

Adding JUnit Library, JUnit5 and Maven Dependencies

Assuming that Selenium Java and WebDriverManager jars are already added, let us add JUnit Library, JUnit5 and Maven dependencies:

Add the following dependency inside the <dependencies> tag in the pom.xml file of the maven project you are using.

<dependency>

     <groupId>org.seleniumhq.selenium</groupId>

     <artifactId>selenium-java</artifactId>

     <version>4.3.0</version>

    </dependency>

<dependency>

    <groupId>io.github.bonigarcia</groupId>

     <artifactId>webdrivermanager</artifactId>

     <version>5.2.1</version>

   </dependency>

<dependency>

<groupId>org.junit.jupiter</groupId>

           <artifactId>junit-jupiter-engine</artifactId>

           <version>5.0.0</version>

           <scope>compile</scope>

</dependency>

Also, add JUnit5 library by right clicking on the Maven project and selecting -> “Build Path” >> “Configure Build Path” >> “Add Library” >> JUnit. Click “Next”, Select “JUnit5” from the “JUnit Library version” dropdown and click on “Finish”. Finally click “Apply and Close” to save the configuration.

JUnit5 Assertions Class Methods

To use JUnit assert methods we need to import org.junit.jupiter.api.Assertions class.

 All JUnit Jupiter Assertions are static methods. As per the official document, “Assertions is a collection of utility methods that support asserting conditions in tests.”

1. assertEquals()

Use Assertions.assertEquals() method, if you need to assert that any given two values are equal.

assertEquals() is an overloaded method for different data types such as byte, char, double, float, int, long, Object, short. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertEquals(int expected, int actual)

assertEquals(Object expected, Object actual)

assertEquals(Object expected, Object actual, String message)      

Program:

public class AssertionsTest {
static WebDriver driver;
static String url = "http://automationpractice.com/index.php";
WebElement wb=driver.findElement(By.xpath("//span[@class='shop-phone']//i[@class='icon-phone']/following-sibling::strong"));

@BeforeAll
public static void setUp() {
WebDriverManager.chromedriver().setup();
driver = new ChromeDriver();
driver.manage().window().maximize();
driver.get(url);
}

@Test
@DisplayName("AsserEquals demo")
public void assertEquals() {
//This will fail
Assertions.assertEquals("0123-23456", wb.getText());
Assertions.assertEquals('S', 'S');
//This will fail
Assertions.assertEquals("JUnit5", "JUnit4", "Strings are not equal");
}
}

In the first assertion, we are expecting “0123-23456” and the actual value is “0123-456-789”. So, the assertion will fail.

In the third assertion, we are expecting “JUnit5”, and actual value is “JUnit4”, so the assert will fail with the message passed.

In case of failure, AssertionFailedError exception will be thrown in the following manner:

2. assertNotEquals()

Use Assertions.assertNotEquals() method, if you need to assert that given any two values are not equal.

assertNotEquals() supports only Object data type as parameter. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertNotEquals (Object unexpected, Object actual)

assertNotEquals (Object unexpected, Object actual, String message)

Program:

@Test
@DisplayName("AsserNotEquals demo")
public void assertNotEquals() {
//This will fail
Assertions.assertNotEquals("0123-456-789", wb.getText());
Assertions.assertNotEquals("JUnit5", "JUnit4");
Assertions.assertNotEquals('S', 'T');
}

In case of failure, AssertionFailedError exception will be thrown in the following manner:

3. assertArrayEquals() 

Use Assertions.assertArrayEquals() method, if you need to assert that given any two arrays are equal.

assertArrayEquals() is an overloaded method for different data types such as boolean[], byte[], char[], double[], float[], int[], long[], Object[], short[]. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertArrayEquals (int expected, int actual)

assertArrayEquals (Object expected, Object actual)

assertArrayEquals (int expected, int actual, String message)    

Program:

@Test
@DisplayName("AssertArrayEquals demo")
public void assertArrayEquals() {
int[] array1 = { 1, 2, 3 };
int[] array2 = { 2, 3, 1 };
//This will fail
Assertions.assertArrayEquals(array1, array2);
}

The assert will fail as element order is different.

In case of failure, AssertionFailedError exception will be thrown in the following manner:

4. assertNull()

Use Assertions.assertNull() method, if you need to assert that given any value is null. 

assertNull() supports only Object data type as parameter. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertNull (Object actual)

assertNull (Object actual, String message)

Program:

@Test
@DisplayName("AssertNull demo")
public void assertNull() {
Assertions.assertNull(null);
//This will fail
Assertions.assertNull(wb.getText());
}

The second assert will fail as we are passing element string value which is not null

In case of failure, AssertionFailedError exception will be thrown in the following manner:

5. assertNotNull()

Use Assertions.assertNotNull() method, if you need to assert that given any value is not null.

assertNotNull() supports only Object data type as parameter. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertNotNull (Object actual)

assertNotNull (Object actual, String message)      

Program:

@Test
@DisplayName("AssertNotNull demo")
public void assertNotNull() {
Assertions.assertNotNull(wb.getText());
//This will fail
Assertions.assertNotNull(null); 
}

The second assert will fail as we are explicitly passing null value.

In case of failure, AssertionFailedError exception will be thrown.

6. assertSame()

Use Assertions.assertSame() method, if you need to assert that given any two values refer to the same object. 

assertSame() supports only Object data type as parameter. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertSame (Object expected, Object actual)

assertSame (Object expected, Object actual, String message)

Program:

@Test
@DisplayName("AssertSame demo")
public void assertSame() {
String s1="JUnit is great!";
String copy=s1;
String s2="JUnit is fun!";
Assertions.assertSame(s1, copy);
//This will fail
Assertions.assertSame(s1, s2);
}

First assert will pass as copy and s1 refer to the same object

Second assert will fail as s1 and s2 refer to the different object

In case of failure, AssertionFailedError exception will be thrown in the following manner:

7. assertNotSame()

Use Assertions.assertNotSame() method, if you need to assert that given any two values do not refer to the same object.

assertNotSame() supports only Object data type as parameter. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertNotSame (Object unexpected, Object actual)

assertNotSame (Object unexpected, Object actual, String message)

Program:

@Test
@DisplayName("AssertNotSame demo")
public void assertNotSame() {
String s1="Selenium";
String copy=s1;
String s2="Playwright";
//This will fail
Assertions.assertNotSame(s1, copy);
Assertions.assertNotSame(s1, s2);
}

First assert will fail as s1 and copy refer to the same object

Second assert will pass as s1 and s2 refer to the different object

In case of failure, AssertionFailedError exception will be thrown in the following manner:

8. assertTrue()

Use Assertions.assertTrue() method, if you need to assert that the supplied condition is true.

assertTrue() supports only boolean value as parameter. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertTrue (boolean condition)

assertTrue (boolean condition, String message)

Program:

@Test
@DisplayName("AssertTrue demo")
public void assertTrue() {
Assertions.assertTrue(true);
//This will fail
Assertions.assertTrue(5 < 0);
Assertions.assertTrue(wb.isDisplayed());
}

Second assert will fail as 5<0 returns false

In case of failure, AssertionFailedError exception will be thrown in the following manner:

9. assertFalse()

Use Assertions.assertFalse() method, if you need to assert that the supplied condition is false.

assertFalse() supports only boolean value as parameter. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertFalse (boolean condition)

assertFalse (boolean condition, String message)

Program:

@Test
@DisplayName("AssertFalse demo")
public void assertFalse() {
Assertions.assertFalse(false);
Assertions.assertFalse(5 < 0);
//This will fail
Assertions.assertFalse(wb.isDisplayed(), "Expected web element not to be displayed");
}

Third assert will fail as element is displayed on webpage which is true value

In case of failure, AssertionFailedError exception will be thrown as seen below:

10. assertIterableEquals()

Use Assertions.assertIterableEquals () method, if you need to assert that the actual and expected iterables are deeply equal. It means the total number of elements and the order of actual and expected should be equal.

assertThrows() supports Iterable object as parameter. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertIterableEquals(Iterable<?> expected, Iterable<?> actual)

assertIterableEquals(Iterable<?> expected, Iterable<?> actual, String message)

Program:

@Test
@DisplayName("AssertIterableEquals demo")
public void assertIterableEquals() {
final List<Integer> firstList = Arrays.asList(1, 2, 3);
final List<Integer> secondList = Arrays.asList(1, 2, 3);
final List<Integer> thirdList = Arrays.asList(3, 1, 2);
Assertions.assertIterableEquals(firstList, secondList);
//This will fail
Assertions.assertIterableEquals(firstList, thirdList);
}

First assert will pass as firstList and secondList have the same number of elements and are in the same order.

Second assert will pass as firstList and thirdList have the same number of elements but are not in the same order.

In case of failure, AssertionFailedError exception will be thrown in the following manner:

11. assertThrows()

Use Assertions.assertThrows() method, if you need to assert that the supplied executable throws an exception of the expected type and returns the exception.

assertThrows() supports only exception classes and executable as parameters. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertThrows (Class<T> expectedType, Executable executable)

assertThrows (Class<T> expectedType, Executable executable, String message)

Program:

@Test
@DisplayName("AssertThrows demo")
public void assertThrows() {

Throwable ex =Assertions.assertThrows(IllegalArgumentException.class,
()-> {throw new IllegalArgumentException();});
//This will fail
Throwable exc=Assertions.assertThrows(IllegalArgumentException.class,
()-> {throw new NullPointerException();});
}

First assert will pass as expected Exception type and the error thrown by the executable are the same.

Second assert will fail as expected Exception type and the error thrown by the executable are different.

In case of failure, AssertionFailedError exception will be thrown in the following manner:

12. assertTimeout()

Use Assertions.assertTimeout() method, if you need to assert that the execution of the system under test is completed before the specified timeout is exceeded.

assertTimeout() supports Duration object, ThrowingSupplier object or an executable. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertTimeout (Duration timeout, Executable executable)

assertTimeout (Duration timeout, Executable executable, String message)

Program:

@Test
@DisplayName("AssertTimeout demo")
public void assertTimeout() {

Assertions.assertTimeout(Duration.ofMinutes(1), ()-> {return "testresult";});
Assertions.assertTimeout(Duration.ofMillis(100), () -> {
Thread.sleep(200);
return "testresult";
});
}

• The first assert will pass as we expect the message to be returned before 1 min. And as there is no delay provided, the message will be returned instantly.
• The second assert will fail as we expect the message to be returned before 100 milliseconds. And as there is a delay of 200 milliseconds before returning the message, it will obviously fail.

In case of failure, AssertionFailedError exception will be thrown in the following manner: 

13. assertTimeoutPreemptively()

In assertTimeoutPreemptively () method, execution of the Executable or ThrowingSupplier will be preemptively aborted if the timeout is exceeded.

assertTimeout() supports Duration object, ThrowingSupplier object or an executable. It also supports error messages to be passed as an argument in case of test failure.

Syntax:

assertTimeoutPreemptively (Duration timeout, Executable executable)

assertTimeout Preemptively (Duration timeout, Executable executable, String message)

Program:

@Test
@DisplayName("AssertTimeoutPreemptively demo")
public void assertTimeoutPreemptively() {
Assertions.assertTimeoutPreemptively(Duration.ofMinutes(1), ()-> {return "testresult";});
Assertions.assertTimeoutPreemptively(Duration.ofMillis(100), () -> {
Thread.sleep(200);
return "testresult";
});
}

In case of failure, AssertionFailedError exception will be thrown in the following manner: 

14. fail()

Use Assertions.fail() method, if you need to fail a particular method with the supplied message as well as the underlying cause of the failure.

fail() supports String and Throwable values as parameters.

Syntax:

fail(String message)

fail(String message, Throwable cause)

Program:

@Test
@DisplayName("Fail demo")
public void Fail() { 
Assertions.fail("This method is failed");
}

In case of failure, AssertionFailedError exception will be thrown in the following manner:

There you have it. 14 different examples on how to use different types of JUnit Assertions for Selenium Tests. Ensure that refer to our documentation while you’re running your first Selenium test with JUnit 5 on BrowserStack Automate

Integrate Selenium with JUnit5

Conclusion

JUnit testing is one of the most preferred testing methods as is powerful and continually evolving for better test case execution. It has become a preferred choice for Test-driven development cycle (TDD).

However, the true potential of such frameworks shines through by running the tests on real browsers and devices under real user conditions. This is where you can count on BrowserStack Cloud Selenium Grid to run the same test on multiple device-browser combinations to reduce time and effort.