JUnit 5 @BeforeEach Annotation Example

JUnit 5 @BeforeEach annotation is replacement of @Before annotation in JUnit 4. It is used to signal that the annotated method should be executed before each @Test method in the current class.

@BeforeEach Annotation Usage

Annotate a method with @BeforeEach as given below:

@BeforeEach
public void initEach(){
	System.out.println("Before Each initEach() method called");
}

@BeforeEach annotated method MUST NOT be a static method otherwise it will throw runtime error.

org.junit.platform.commons.JUnitException: @BeforeEach method 'public static void com.howtodoinjava.junit5.examples.JUnit5AnnotationsExample.initEach()' must not be static.
	at org.junit.jupiter.engine.descriptor.LifecycleMethodUtils.assertNonStatic(LifecycleMethodUtils.java:73)
	at org.junit.jupiter.engine.descriptor.LifecycleMethodUtils.lambda$findBeforeEachMethods$2(LifecycleMethodUtils.java:54)
	at java.util.ArrayList.forEach(ArrayList.java:1249)
	at java.util.Collections$UnmodifiableCollection.forEach(Collections.java:1080)
	at org.junit.jupiter.engine.descriptor.LifecycleMethodUtils.findBeforeEachMethods(LifecycleMethodUtils.java:54)

@BeforeEach 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. For every run of test method, @BeforeEach annotated method should also run every time.

package com.howtodoinjava.junit5.examples;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.RepeatedTest;
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 JUnit5AnnotationsExample {

	@Test
	@DisplayName("Add operation test")
	@RepeatedTest(5)
	void addNumber(TestInfo testInfo) {
		Calculator calculator = new Calculator();
		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");
	}
	
	@BeforeEach
	public void initEach(){
		System.out.println("Before Each initEach() method called");
	}
}

Where Calculator class is:

package com.howtodoinjava.junit5.examples;

public class Calculator 
{
	public 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
Before Each initEach() method called
Before Each initEach() method called
Before Each initEach() method called
Before Each initEach() method called
Before Each initEach() method called
Before Each initEach() method called

Clearly, @BeforeEach annotated initEach() method is called once per test method invocation.

Happy Learning !!