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.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 BeforeEachTest {

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

BeforeAll init() method called
BeforeEach initEach() method called

BeforeEach initEach() method called
Running test -> 1

BeforeEach initEach() method called
Running test -> 2

BeforeEach initEach() method called
Running test -> 3

BeforeEach initEach() method called
Running test -> 4

BeforeEach initEach() method called
Running test -> 5

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

Happy Learning !!