JUnit 5 @BeforeAll annotation example

JUnit 5 @BeforeAll annotation is replacement of @BeforeClass annotation in JUnit 4. It is used to signal that the annotated method should be executed before all tests in the current test class.

@BeforeAll Annotation Usage

Annotate a method with @BeforeAll as given below:

@BeforeAll
public static void init(){
	System.out.println("BeforeAll init() method called");
}

@BeforeAll annotated method MUST be a static method otherwise it will throw runtime error.

org.junit.platform.commons.JUnitException: @BeforeAll method 'public void com.howtodoinjava.junit5.examples.JUnit5AnnotationsExample.init()' must be static.
at org.junit.jupiter.engine.descriptor.LifecycleMethodUtils.assertStatic(LifecycleMethodUtils.java:66)
at org.junit.jupiter.engine.descriptor.LifecycleMethodUtils.lambda$findBeforeAllMethods$0(LifecycleMethodUtils.java:42)
at java.util.ArrayList.forEach(ArrayList.java:1249)
at java.util.Collections$UnmodifiableCollection.forEach(Collections.java:1080)
at org.junit.jupiter.engine.descriptor.LifecycleMethodUtils.findBeforeAllMethods(LifecycleMethodUtils.java:42)

@BeforeAll Annotation Example

Let’s take an example. I have used one Calculator class and added one add method. I will test it 5 times using @RepeatedTest annotation. This annotation will cause the add test to run 5 times. But @BeforeAll annotated method must be called only once.

package com.howtodoinjava.junit5.examples;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.RepeatedTest;
import org.junit.jupiter.api.RepetitionInfo;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInfo;
import org.junit.platform.runner.JUnitPlatform;
import org.junit.runner.RunWith;

@RunWith(JUnitPlatform.class)
public class BeforeAllTest {

	@DisplayName("Add operation test")
	@RepeatedTest(5)
	void addNumber(TestInfo testInfo, RepetitionInfo repetitionInfo) {
		System.out.println("Running test -> " + repetitionInfo.getCurrentRepetition());
		Assertions.assertEquals(2, Calculator.add(1, 1), "1 + 1 should equal 2");
	}
	
	@BeforeAll
	public static void init(){
		System.out.println("Before All init() method called");
	}
}

Where Calculator class is:

package com.howtodoinjava.junit5.examples;

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

Now execute the test and you will see below console output:

Before All init() method called
Running test -> 1
Running test -> 2
Running test -> 3
Running test -> 4
Running test -> 5

Clearly, @BeforeAll annotated init() method is called only once.

Happy Learning !!

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