我有一些正在测试的代码,它调用Java记录器来报告其状态。
在JUnit测试代码中,我想验证在这个日志记录器中创建了正确的日志条目。大致如下:
methodUnderTest(bool x){
if(x)
logger.info("x happened")
}
@Test tester(){
// perhaps setup a logger first.
methodUnderTest(true);
assertXXXXXX(loggedLevel(),Level.INFO);
}
我认为这可以用一个经过特别调整的记录器(或处理程序或格式化程序)来完成,但我更愿意重用现有的解决方案。(而且,老实说,我不清楚如何从记录器获得logRecord,但假设这是可能的。)
我为log4j回答了一个类似的问题,请参阅how-can-i-test-with-junit-that-a-warning-was-logged-with-log4
这是更新的Log4j2(用2.11.2测试)和junit 5的示例;
package com.whatever.log;
import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.core.Logger;
import org.apache.logging.log4j.core.*;
import org.apache.logging.log4j.core.appender.AbstractAppender;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.LoggerConfig;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginElement;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import java.util.ArrayList;
import java.util.List;
import static org.junit.Assert.*;
class TestLogger {
private TestAppender testAppender;
private LoggerConfig loggerConfig;
private final Logger logger = (Logger)
LogManager.getLogger(ClassUnderTest.class);
@Test
@DisplayName("Test Log Junit5 and log4j2")
void test() {
ClassUnderTest.logMessage();
final LogEvent loggingEvent = testAppender.events.get(0);
//asset equals 1 because log level is info, change it to debug and
//the test will fail
assertTrue(testAppender.events.size()==1,"Unexpected empty log");
assertEquals(Level.INFO,loggingEvent.getLevel(),"Unexpected log level");
assertEquals(loggingEvent.getMessage().toString()
,"Hello Test","Unexpected log message");
}
@BeforeEach
private void setup() {
testAppender = new TestAppender("TestAppender", null);
final LoggerContext context = logger.getContext();
final Configuration configuration = context.getConfiguration();
loggerConfig = configuration.getLoggerConfig(logger.getName());
loggerConfig.setLevel(Level.INFO);
loggerConfig.addAppender(testAppender,Level.INFO,null);
testAppender.start();
context.updateLoggers();
}
@AfterEach
void after(){
testAppender.stop();
loggerConfig.removeAppender("TestAppender");
final LoggerContext context = logger.getContext();
context.updateLoggers();
}
@Plugin( name = "TestAppender", category = Core.CATEGORY_NAME, elementType = Appender.ELEMENT_TYPE)
static class TestAppender extends AbstractAppender {
List<LogEvent> events = new ArrayList();
protected TestAppender(String name, Filter filter) {
super(name, filter, null);
}
@PluginFactory
public static TestAppender createAppender(
@PluginAttribute("name") String name,
@PluginElement("Filter") Filter filter) {
return new TestAppender(name, filter);
}
@Override
public void append(LogEvent event) {
events.add(event);
}
}
static class ClassUnderTest {
private static final Logger LOGGER = (Logger) LogManager.getLogger(ClassUnderTest.class);
public static void logMessage(){
LOGGER.info("Hello Test");
LOGGER.debug("Hello Test");
}
}
}
使用以下maven依赖项
<dependency>
<artifactId>log4j-core</artifactId>
<packaging>jar</packaging>
<version>2.11.2</version>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-api</artifactId>
<version>5.5.0</version>
<scope>test</scope>
</dependency>
I also ran into the same challanged and ended up at this page. Although I am 11 years too late to answers the question, I thought maybe it could be still usefull for others. I found the answer of davidxxx with Logback and the ListAppander very usefull. I used the same configuration for multiple projects, however it was not so fun to copy/paste it and maintaining all the version when I needed to changes something. I thought it would be better to make a library out of it and contribute back to the community. It works with SLFJ4, Log4j, Log4j2, Java Util Logging, JBoss Logging and with Lombok annotations. Please have a look here: LogCaptor for detailed examples and how to add it to your project.
示例情况:
public class FooService {
private static final Logger LOGGER = LoggerFactory.getLogger(FooService.class);
public void sayHello() {
LOGGER.warn("Congratulations, you are pregnant!");
}
}
使用LogCaptor的单元测试示例:
import nl.altindag.log.LogCaptor;
import org.junit.jupiter.api.Test;
import static org.assertj.core.api.Assertions.assertThat;
public class FooServiceTest {
@Test
public void sayHelloShouldLogWarnMessage() {
LogCaptor logCaptor = LogCaptor.forClass(FooService.class);
FooService fooService = new FooService();
fooService.sayHello();
assertThat(logCaptor.getWarnLogs())
.contains("Congratulations, you are pregnant!");
}
}
我不太确定是否应该在这里发布这篇文章,因为这也可以被视为推广“我的库”的一种方式,但我认为这对面临同样挑战的开发人员有帮助。
非常感谢这些(令人惊讶的)快速而有用的回答;他们让我找到了正确的解决方法。
我想要使用的代码库使用java.util.logging作为其记录器机制,我对这些代码感到不够熟悉,无法完全将其更改为log4j或记录器接口/facade。但基于这些建议,我“破解”了一个j.u.l handler扩展,这是一种享受。
下面是一个简短的总结。延长java.util.logging.Handler:
class LogHandler extends Handler
{
Level lastLevel = Level.FINEST;
public Level checkLevel() {
return lastLevel;
}
public void publish(LogRecord record) {
lastLevel = record.getLevel();
}
public void close(){}
public void flush(){}
}
显然,您可以从LogRecord中存储您喜欢/想要/需要的任何数量,或者将它们全部推入堆栈,直到溢出。
在junit-test的准备过程中,你创建了一个java.util.logging.Logger,并添加这样一个新的LogHandler:
@Test tester() {
Logger logger = Logger.getLogger("my junit-test logger");
LogHandler handler = new LogHandler();
handler.setLevel(Level.ALL);
logger.setUseParentHandlers(false);
logger.addHandler(handler);
logger.setLevel(Level.ALL);
对setUseParentHandlers()的调用将使正常的处理程序静默,以便(对于这个junit-test运行)不会发生不必要的日志记录。做任何你的测试代码需要使用这个记录器,运行测试和assertEquality:
libraryUnderTest.setLogger(logger);
methodUnderTest(true); // see original question.
assertEquals("Log level as expected?", Level.INFO, handler.checkLevel() );
}
(当然,您可以将大部分工作移到@Before方法中,并进行各种其他改进,但这会使演示变得混乱。)
Log4J2的API略有不同。你也可以使用它的async appender。我为此创建了一个锁定的appender:
public static class LatchedAppender extends AbstractAppender implements AutoCloseable {
private final List<LogEvent> messages = new ArrayList<>();
private final CountDownLatch latch;
private final LoggerConfig loggerConfig;
public LatchedAppender(Class<?> classThatLogs, int expectedMessages) {
this(classThatLogs, null, null, expectedMessages);
}
public LatchedAppender(Class<?> classThatLogs, Filter filter, Layout<? extends Serializable> layout, int expectedMessages) {
super(classThatLogs.getName()+"."+"LatchedAppender", filter, layout);
latch = new CountDownLatch(expectedMessages);
final LoggerContext ctx = (LoggerContext) LogManager.getContext(false);
final Configuration config = ctx.getConfiguration();
loggerConfig = config.getLoggerConfig(LogManager.getLogger(classThatLogs).getName());
loggerConfig.addAppender(this, Level.ALL, ThresholdFilter.createFilter(Level.ALL, null, null));
start();
}
@Override
public void append(LogEvent event) {
messages.add(event);
latch.countDown();
}
public List<LogEvent> awaitMessages() throws InterruptedException {
assertTrue(latch.await(10, TimeUnit.SECONDS));
return messages;
}
@Override
public void close() {
stop();
loggerConfig.removeAppender(this.getName());
}
}
像这样使用它:
try (LatchedAppender appender = new LatchedAppender(ClassUnderTest.class, 1)) {
ClassUnderTest.methodThatLogs();
List<LogEvent> events = appender.awaitMessages();
assertEquals(1, events.size());
//more assertions here
}//appender removed
另一个选项是模拟Appender并验证消息是否已记录到此Appender。Log4j 1.2的示例。X和mockito:
import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import org.apache.log4j.Appender;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.apache.log4j.spi.LoggingEvent;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.mockito.ArgumentCaptor;
public class MyTest {
private final Appender appender = mock(Appender.class);
private final Logger logger = Logger.getRootLogger();
@Before
public void setup() {
logger.addAppender(appender);
}
@Test
public void test() {
// when
Logger.getLogger(MyTest.class).info("Test");
// then
ArgumentCaptor<LoggingEvent> argument = ArgumentCaptor.forClass(LoggingEvent.class);
verify(appender).doAppend(argument.capture());
assertEquals(Level.INFO, argument.getValue().getLevel());
assertEquals("Test", argument.getValue().getMessage());
assertEquals("MyTest", argument.getValue().getLoggerName());
}
@After
public void cleanup() {
logger.removeAppender(appender);
}
}