JUnit 5 @BeforeAll Annotation with Examples

JUnit 5 is the unit testing framework in Java, and it is not a tool rather the JUnit 5 framework contains a set of tools and libraries that are used to write and run test cases. The Junit 5 Framework was introduced in 2017, This was developed by Kent Beck, Erich Gamma, David Saff, and Kris Vasudevan. Its Operating System is cross-platform and this framework is written in Java. This Framework makes it easier to extend the framework, and we can able integrate with other testing frameworks also, In JUnit 5 several new Annotations are introduced those are @BeforeAll, @AfterAll, @BeforeEach, @AfterEach, @TestFactory, @DisplayName, @Disabled, @Nested, @Tag. Among these annotations, I give Information about @BeforeAll annotation.

Features of JUnit 5

There are certain features of JUnit 5 as mentioned below:

• Supporting Java 8 Features like
• Introduced new test organization features like tags & categories
• JUnit 5 Framework Support Parallel test execution
• It can support the New Extension Model and also
• It can support parameterized tests
• This framework supports Assumptions

Note : If you want use JUnit 5 in your Project for write and run tests, It requires Java 8 or higher Runtime

@BeforeAll in JUnit 5

@BeforeAll is an annotation that is announced in the JUnit 5 framework, The @BeforeAll is used to signal that the annotated method should be executed before all test cases. And @BeforeAll methods are executed only once for assigned test cases. One more thing is that it should be used with the static method in the test class.
Now I provide the basic syntax of the @BeforeAll annotation below please follow the syntax for better understanding.

Basic Syntax

class GFG {
   @BeforeAll
  public static void Test1(){
     // your own testing code here
   }
 
  @Test
  public void test2(){
    // your code 
   }
}

If you want to work with @BeforeAll then you need to have strong knowledge of JUnit 4.

Note: In the above syntax we use the static method for @BeforeAll.

Prerequisites for the Topic

• Method Signature: @BeforeAll methods must have a void return type and it is a static type.
• Test classes: @BeforeAll methods are not supported in nested test classes.
• Execution: @BeforeAll executed only once for assigned test cases.

Note : @BeforeAll methods mush have return type void and must not be private.

Examples of JUnit 5 - @BeforeAll

Example 1 :

Let us take an example, we have written a test for the String Handler class to check whether the given string is empty or not

//Class to test String trim method
public class StringHandler {
  
    //To Perform operations on the input string
    public static String manipulateString(String input) {
        
          // Trim the input string
        return input.trim(); 
    }
}

Now we write a test case for it to check whether the given String is empty or not

In the above code, I take a string value and remove white spaces by using the trim() string function then return that string value.

// Testing file to test the manipulate
// String Class 

import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertTrue;

//Testing Class
public class StringTest {

    private static String testString;

    // This method is executed once before any of the test methods in the class
    @BeforeAll
    static void init() {
      
        // Manipulate the input string and store it in the testString variable
        testString = StringHandler.manipulateString("  Hello, GFG!  ");
      
        // Print the manipulated test string
        System.out.println("Test String: '" + testString + "'");
    }
  

    // Test whether the manipulated string is not empty
    @Test
    void testStringNotEmpty() {
      
        // Print a message indicating that the testStringNotEmpty test is being run
        System.out.println("Running testStringNotEmpty...");
      
        // Assert that the manipulated test string is not empty
        assertTrue(!testString.isEmpty(), "The string should not be empty");
    }

    // Test whether an empty string is indeed empty
    @Test
    void testStringEmpty() {
      
        // Print a message indicating that the testStringEmpty test is being run
        System.out.println("Running testStringEmpty...");
      
        // Create an empty string for the test and assert that it is empty
        String emptyString = "";
        assertTrue(emptyString.isEmpty(), "The string should be empty");
    }
}

Output:

Test String: 'Hello, GFG!'
Running testStringNotEmpty...
Running testStringEmpty...

Explanation of the above Program:

In the above code, I created one static method for @BeforeAll,

• this static method is mandatory for work with @BeforeAll annotation.
• The @BeforeAll is checked first before all test cases are run.
• Only once after that, I create the testStringNotEmpty() function testing if the string is empty or not then return the Running testStringNotEmpty as output.
• After that, I created another testStringEmpty() method for if the string is empty it will return Running testStringEmpty() as an output you can observe the below output.

Example 2 :

Simple Java class to check whether a person is eligible to vote or not based on their age.

//Class to determine VotingEligibility

public class VotingEligibility {

      //Biz-logic for VotingEligibility method
    public static String checkEligibility(int age) { 
      
      // checking the age of the person
        if (age >= 18) {
          
          // if age is elibible then this block executed
            System.out.println("Person is eligible to vote.");
            return "Eligible to vote";
        } 
          else {
        
          // if age is not eligible then this code is executed
            System.out.println("Person is not eligible to vote.");
            return "Not eligible to vote";
        }
    }
}

• In the above code, I try to check whether the person is eligible to Vote or not based on the above condition (age >=18).
• If the person's age is less than 18 then the else block is executed.
• If the age is greater than 18 then the if block code is executed and print the Appropriate Output.

//TESTING file to test the VotingEligibility Class

import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

//Testing class for VotingEligibility
public class VotingEligibilityTest {

    // Variables to store the results of the voting eligibility checks
    private static String resultEligible;
    private static String resultNotEligible;

    // Method to perform setup operations before any of the test methods in the class
    @BeforeAll
    static void init() {
        // Check the eligibility for a person with age 25 and store the result
        resultEligible = VotingEligibility.checkEligibility(25);
        // Check the eligibility for a person with age 16 and store the result
        resultNotEligible = VotingEligibility.checkEligibility(16);
    }

    // Test method to check if a person is eligible to vote
    @Test
    void testEligibleToVote() {
        // Print a message indicating that the testEligibleToVote test is being run
        System.out.println("Running testEligibleToVote...");
        // Assert that a person with age 25 is eligible to vote
        assertEquals("Eligible to vote", resultEligible, "Should be eligible to vote");
    }

    // Test method to check if a person is not eligible to vote
    @Test
    void testNotEligibleToVote() {
        // Print a message indicating that the testNotEligibleToVote test is being run
        System.out.println("Running testNotEligibleToVote...");
        // Assert that a person with age 16 is not eligible to vote
        assertEquals("Not eligible to vote", resultNotEligible, "Should not be eligible to vote");
    }
}

Output:

Person is eligible to vote.
Person is not eligible to vote.
Running testEligibleToVote...
Running testNotEligibleToVote...

Explanation of the above Program:

In the above code, I created three methods for testing purposes the static method is for @BeforeAll annotation.

• The testEligibleToVote() method is used to check whether a person is greater than 18 or not if it is true then this returns output as Running testEligibleToVote.
• The other method is used for testNotEligibleToVote() is used for printing messages if the given age is not eligible to vote.

Importance Of Testing using JUnit

1. Identifying Bugs and Issues
2. Ensuring Software Quality
3. Enhancing User Experience
4. Maintaining Product Reputation
5. Reducing Costs and Risks
6. Compliance and Standards
7. Facilitating Maintenance and Updates

Junit 5 vs Junit 4

The below table explains the major differences between the most widely used versions of JUnit 5 and JUnit 4.

Advantages of @BeforeAll

The @BeforeAll annotation in JUnit provides several advantages in the context of testing are mentioned below:

• Initialization of Resources
• Efficiency
• Improved Test Performance
• Shared State
• Clean Code
• Reduction of Code Duplication
• Support for Stateless Testing
• Explicit Order of Execution
• Scalability

Conclusion

The @BeforeAll annotation is used in JUnit 5 to give a signal that annotated method executes first in that test class before all the test methods.

• This is used for setting data for all the test cases.
• The @BeforeAll have a void return type and should not be private
• @BeforeAll methods can be used in conjunctions with @AfterAll Annotation to perform cleanup tasks.