Maven测试中JUnit5的@BeforeAll/@BeforeEach日志无法输出至控制台问题

我创建了一个简单的Maven项目来复现问题，相关代码和配置如下：

POM文件 #

<?xml version="1.0" encoding="UTF-8"?>
<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>org.example</groupId>
  <artifactId>NoLog</artifactId>
  <version>1.0-SNAPSHOT</version>
  <properties>
    <maven.compiler.source>8</maven.compiler.source>
    <maven.compiler.target>8</maven.compiler.target>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter-engine</artifactId>
      <version>5.9.0</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>commons-logging</groupId>
      <artifactId>commons-logging</artifactId>
      <version>1.2</version>
    </dependency>
    <dependency>
      <groupId>org.apache.logging.log4j</groupId>
      <artifactId>log4j-api</artifactId>
      <version>2.19.0</version>
    </dependency>
    <dependency>
      <groupId>org.apache.logging.log4j</groupId>
      <artifactId>log4j-core</artifactId>
      <version>2.19.0</version>
    </dependency>
    <dependency>
      <groupId>org.apache.logging.log4j</groupId>
      <artifactId>log4j-jcl</artifactId>
      <version>2.19.0</version>
    </dependency>
  </dependencies>
</project>

测试类代码 #

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

public class TestDemo {

  static Logger log = LogManager.getLogger(TestDemo.class);
  @BeforeAll
  public static void setupClass() {
    log.info("BeforeAll 111 from log.info");
    System.out.println("BeforeAll 111 from print");
    log.info("BeforeAll 222 from log.info");
    System.out.println("BeforeAll 222 from print");
  }

  @BeforeEach
  public void setup() {
    log.info("BeforeEach 111 from log.info");
    System.out.println("BeforeEach 111 from print");
    log.info("BeforeEach 222 from log.info");
    System.out.println("BeforeEach 222 from print");
  }

  @Test
  public void test1() {
    log.info("test1 111 from log.info");
    System.out.println("test 111 from print");
    log.info("test1 222 from log.info");
    System.out.println("test 222 from print");
  }
}

Log4j2配置文件 #

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
  <Appenders>
    <Console name="LogToConsole" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{YYYY-MM-dd HH:mm:ss} [%t] %-5p %c{1}:%L - %msg%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Root level="info">
      <AppenderRef ref="LogToConsole"/>
    </Root>
    <Logger name="com.hexagon" level="debug" additivity="false">
      <AppenderRef ref="LogToConsole"/>
    </Logger>
  </Loggers>
</Configuration>

运行结果 #

执行mvn test命令后，仅能看到@Test方法中的日志和输出，@BeforeAll和@BeforeEach中的内容完全不显示：

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running TestDemo
2023-01-05 09:28:03 [main] INFO  TestDemo:29 - test1 111 from log.info
test 111 from print
2023-01-05 09:28:03 [main] INFO  TestDemo:31 - test1 222 from log.info
test 222 from print
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.004 sec

Results :

Tests run: 1, Failures: 0, Errors: 0, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS

核心问题 #

执行mvn test命令时，仅能看到@Test方法中的日志，而@BeforeAll和@BeforeEach中的日志无法输出到控制台，请问原因是什么？如何开启这些日志的输出？

1. Maven Surefire插件版本过低：默认Maven使用的Surefire插件版本可能不兼容JUnit 5，对@BeforeAll、@BeforeEach这类生命周期方法的输出捕获支持不完善，导致这些方法中的输出（包括日志和System.out）被丢弃。
2. Log4j2初始化延迟：Log4j2默认采用懒加载初始化，第一次调用日志方法时才会加载配置文件。@BeforeAll作为静态方法，执行时机可能早于Log4j2完成初始化的时间，导致早期日志事件无法被正确输出。

1. 升级并配置Maven Surefire插件 #

在POM文件中添加最新版本的Surefire插件，并指定使用JUnit 5引擎：

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <version>3.2.5</version>
            <dependencies>
                <dependency>
                    <groupId>org.junit.platform</groupId>
                    <artifactId>junit-platform-surefire-provider</artifactId>
                    <version>1.9.3</version>
                </dependency>
                <dependency>
                    <groupId>org.junit.jupiter</groupId>
                    <artifactId>junit-jupiter-engine</artifactId>
                    <version>5.9.3</version>
                </dependency>
            </dependencies>
        </plugin>
    </plugins>
</build>

2. 提前初始化Log4j2 #

在测试类的静态代码块中主动触发Log4j2的初始化，确保@BeforeAll执行前配置已加载：

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.LoggerContext;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

public class TestDemo {

  static Logger log;
  
  static {
      // 主动初始化Log4j2
      LoggerContext context = (LoggerContext) LogManager.getContext(false);
      context.reconfigure();
      log = LogManager.getLogger(TestDemo.class);
  }

  @BeforeAll
  public static void setupClass() {
    log.info("BeforeAll 111 from log.info");
    System.out.println("BeforeAll 111 from print");
    log.info("BeforeAll 222 from log.info");
    System.out.println("BeforeAll 222 from print");
  }

  // 其余代码不变
}

3. 确保Log4j2配置文件位置正确 #

将log4j2.xml放置在src/test/resources目录下，确保测试类加载时能读取到配置文件。

内容的提问来源于stack exchange，提问作者Reed_Xia