How to Use @BeforeAll in JUnit for Setup Before All Tests

Use @BeforeAll in JUnit to run a method once before all test methods in a class. The method must be static and is typically used to set up shared resources or configurations.

Syntax

The @BeforeAll annotation marks a method to be run once before any test methods in the class. The method must be static and have no parameters.

• @BeforeAll: Annotation to run method once before all tests.
• static void methodName(): Method signature must be static and void.

java

import org.junit.jupiter.api.BeforeAll;

public class TestClass {
    @BeforeAll
    static void setup() {
        // code to run once before all tests
    }
}

Example

This example shows a test class where @BeforeAll initializes a shared resource once before all tests run.

java

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

public class CalculatorTest {
    static Calculator calculator;

    @BeforeAll
    static void init() {
        calculator = new Calculator();
        System.out.println("Setup before all tests");
    }

    @Test
    void testAdd() {
        assertEquals(5, calculator.add(2, 3));
    }

    @Test
    void testSubtract() {
        assertEquals(1, calculator.subtract(3, 2));
    }
}

class Calculator {
    int add(int a, int b) {
        return a + b;
    }

    int subtract(int a, int b) {
        return a - b;
    }
}

Output

Setup before all tests

[INFO] Tests run: 2, Failures: 0, Errors: 0, Skipped: 0

Common Pitfalls

• Forgetting to make the @BeforeAll method static causes runtime errors.
• Using @BeforeAll in non-static context without enabling test instance lifecycle PER_CLASS will fail.
• Trying to use parameters in @BeforeAll methods is not allowed.

java

import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;

public class WrongTest {
    // This will cause an error because method is not static
    @BeforeAll
    void setup() {
        System.out.println("This will fail");
    }

    @Test
    void testSomething() {
        // test code
    }
}

// Correct way:

import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;

public class CorrectTest {
    @BeforeAll
    static void setup() {
        System.out.println("This works");
    }

    @Test
    void testSomething() {
        // test code
    }
}

Quick Reference

• @BeforeAll: Run once before all tests in the class.
• Method must be static unless using @TestInstance(TestInstance.Lifecycle.PER_CLASS).
• Use for expensive setup like database connections or shared resources.
• Runs before any @BeforeEach methods.

Key Takeaways

Use @BeforeAll to run setup code once before all tests in a class.

The method annotated with @BeforeAll must be static unless using PER_CLASS lifecycle.

Common mistake: forgetting static causes test failures.

Use @BeforeAll for initializing shared resources or expensive setup.

It runs before any @BeforeEach methods in the test lifecycle.