JUnit 5 does not execute method annotated with BeforeEach

问题

JUnit 5 does not invoke my method in a test class that is annotated with the @BeforeEach annotation, where I initialize some fields of the test object that are needed in the tests. When trying to access these fields inside a test method (method annotated with @Test) I obviously get a NullpointerException. So I added some output messages to the methods.

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

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

public class TestClass {
   private String s;

   public TestClass() {

   }

   @BeforeEach
   public void init() {
      System.out.println("before");
      s = "not null";
   }

   @Test
   public void test0() {
      System.out.println("testing");
      assertEquals("not null", s.toString());
   }

}

In the output of the tests when running mvn clean test I get the "testing" message from the test0() method annotated with @Test annotation, but the "before" message is not printed.

Running de.dk.spielwiese.TestClass
!!!testing!!!
Tests run: 1, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0 sec <<< FAILURE!
de.dk.spielwiese.TestClass.test0()  Time elapsed: 0 sec  <<< FAILURE!
java.lang.NullPointerException
        at de.dk.spielwiese.TestClass.test0(TestClass.java:24)

The very obvious and only reason that I can think of is that the init() method is not invoked. The documentation of @BeforeEach says

@BeforeEach is used to signal that the annotated method should be executed before each @Test, @RepeatedTest, @ParameterizedTest, @TestFactory, and @TestTemplate method in the current test class.

I also tried running the tests in eclipse and there they always pass without any errors.

I am using maven 3.5.3. I declared JUnit Jupiter 5.1.0 as dependency in my pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>de.dk</groupId>
<artifactId>spielwiese</artifactId>
<version>0-SNAPSHOT</version>
<packaging>jar</packaging>

<name>Spielwiese</name>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<build>
    <plugins>
        <plugin>
            <artifactId>maven-assembly-plugin</artifactId>
            <version>3.0.0</version>
            <configuration>
                <archive>
                    <manifest>
                        <mainClass>de.dk.spielwiese.Spielwiese</mainClass>
                    </manifest>
                </archive>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
                <appendAssemblyId>false</appendAssemblyId>
                <finalName>Spielwiese</finalName>
            </configuration>
            <executions>
                <execution>
                    <id>assemble-all</id>
                    <phase>package</phase>
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.6.2</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
        <plugin>
            <artifactId>maven-jar-plugin</artifactId>
            <version>3.0.2</version>
        </plugin>
    </plugins>
</build>

<dependencies>
    <dependency>
        <groupId>de.dk</groupId>
        <artifactId>util</artifactId>
        <version>0.0.1</version>
    </dependency>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-engine</artifactId>
        <version>5.1.0</version>
        <scope>test</scope>
    </dependency>
</dependencies>

Why is my init() method not invoked?

回答1:

Your init() method is not invoked because you have not instructed Maven Surefire to use the JUnit Platform Surefire Provider.

Thus, surprisingly your test is not even being run with JUnit. Instead, it is being run with Maven Surefire's support for what they call POJO Tests.

Adding the following to your pom.xml should solve the problem.

<build>
    <plugins>
        <plugin>
            <artifactId>maven-surefire-plugin</artifactId>
            <version>2.19.1</version>
            <dependencies>
                <dependency>
                    <groupId>org.junit.platform</groupId>
                    <artifactId>junit-platform-surefire-provider</artifactId>
                    <version>1.1.0</version>
                </dependency>
            </dependencies>
        </plugin>
    </plugins>
</build>

回答2:

Sam Brannen's answer worked for me, but it seems that it doesn't work with the 2.22.0 version of maven-surefire-plugin unless you upgrade the junit-platform-surefire-provider to 1.2.0. Be aware!

回答3:

There is junit-jupiter-api dependency missing

<dependencies>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-api</artifactId>
        <version>5.5.1</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-engine</artifactId>
        <version>5.5.1</version>
        <scope>test</scope>
    </dependency>
</dependencies>

<plugins>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>2.22.1</version>
    </plugin>
</plugins>

回答4:

Nowadays it is not necessary to add provider to plugin. Just add junit-jupiter-engine to your dependencies (as written in official documentation https://maven.apache.org/surefire/maven-surefire-plugin/examples/junit-platform.html).

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-engine</artifactId>
    <version>5.3.1</version>
    <scope>test</scope>
</dependency>

来源：https://stackoverflow.com/questions/49441049/junit-5-does-not-execute-method-annotated-with-beforeeach