@BeforeAll method in JUnit

Introduction

The @BeforeAll method runs once before all tests. It helps set up things needed for every test, saving time and avoiding repetition.

When you need to open a database connection once before all tests run.

When you want to initialize shared test data or configuration.

When you want to start a server or service once before running tests.

When you want to load a file or resource only once for all tests.

Syntax

JUnit

@BeforeAll
static void methodName() {
    // setup code here
}

The method must be static in JUnit 5.

This method runs only once before any test methods.

Examples

This prints a message once before all tests.

JUnit

@BeforeAll
static void setup() {
    System.out.println("Setup before all tests");
}

Initialize database connection once before tests.

JUnit

@BeforeAll
static void initDatabase() {
    // code to connect to database
}

Sample Program

This test class uses @BeforeAll to set a flag once. Both tests check the flag is true and print messages.

JUnit

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

public class SampleTest {

    static boolean isSetupDone = false;

    @BeforeAll
    static void setup() {
        System.out.println("Running setup once");
        isSetupDone = true;
    }

    @Test
    void testOne() {
        assertTrue(isSetupDone);
        System.out.println("Test One running");
    }

    @Test
    void testTwo() {
        assertTrue(isSetupDone);
        System.out.println("Test Two running");
    }
}

Important Notes

If the @BeforeAll method is not static, tests will fail to run.

Use @BeforeAll only for setup that applies to all tests.

Summary

@BeforeAll runs once before all tests.

The method must be static in JUnit 5.

Use it to prepare shared resources or setup.