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。)
当前回答
这里有一个简单有效的Logback解决方案。 它不需要添加/创建任何新类。 它依赖于ListAppender:一个白盒回logback appender，其中将日志条目添加到公共List字段中，我们可以使用该字段来进行断言。
这里有一个简单的例子。
Foo类:
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class Foo {
static final Logger LOGGER = LoggerFactory.getLogger(Foo .class);
public void doThat() {
LOGGER.info("start");
//...
LOGGER.info("finish");
}
}
FooTest类:
import org.slf4j.LoggerFactory;
import ch.qos.logback.classic.Level;
import ch.qos.logback.classic.Logger;
import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.core.read.ListAppender;
public class FooTest {
@Test
void doThat() throws Exception {
// get Logback Logger
Logger fooLogger = (Logger) LoggerFactory.getLogger(Foo.class);
// create and start a ListAppender
ListAppender<ILoggingEvent> listAppender = new ListAppender<>();
listAppender.start();
// add the appender to the logger
// addAppender is outdated now
fooLogger.addAppender(listAppender);
// call method under test
Foo foo = new Foo();
foo.doThat();
// JUnit assertions
List<ILoggingEvent> logsList = listAppender.list;
assertEquals("start", logsList.get(0)
.getMessage());
assertEquals(Level.INFO, logsList.get(0)
.getLevel());
assertEquals("finish", logsList.get(1)
.getMessage());
assertEquals(Level.INFO, logsList.get(1)
.getLevel());
}
}
JUnit断言听起来不太适合断言列表元素的某些特定属性。 像AssertJ或Hamcrest这样的Matcher/断言库似乎更好:
使用AssertJ，它将是:
import org.assertj.core.api.Assertions;
Assertions.assertThat(listAppender.list)
.extracting(ILoggingEvent::getMessage, ILoggingEvent::getLevel)
.containsExactly(Tuple.tuple("start", Level.INFO), Tuple.tuple("finish", Level.INFO));
其他回答
这里有一个很好的和优雅的方法来解决这个问题: https://www.baeldung.com/junit-asserting-logs
这里有一个简单有效的Logback解决方案。 它不需要添加/创建任何新类。 它依赖于ListAppender:一个白盒回logback appender，其中将日志条目添加到公共List字段中，我们可以使用该字段来进行断言。
这里有一个简单的例子。
Foo类:
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class Foo {
static final Logger LOGGER = LoggerFactory.getLogger(Foo .class);
public void doThat() {
LOGGER.info("start");
//...
LOGGER.info("finish");
}
}
FooTest类:
import org.slf4j.LoggerFactory;
import ch.qos.logback.classic.Level;
import ch.qos.logback.classic.Logger;
import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.core.read.ListAppender;
public class FooTest {
@Test
void doThat() throws Exception {
// get Logback Logger
Logger fooLogger = (Logger) LoggerFactory.getLogger(Foo.class);
// create and start a ListAppender
ListAppender<ILoggingEvent> listAppender = new ListAppender<>();
listAppender.start();
// add the appender to the logger
// addAppender is outdated now
fooLogger.addAppender(listAppender);
// call method under test
Foo foo = new Foo();
foo.doThat();
// JUnit assertions
List<ILoggingEvent> logsList = listAppender.list;
assertEquals("start", logsList.get(0)
.getMessage());
assertEquals(Level.INFO, logsList.get(0)
.getLevel());
assertEquals("finish", logsList.get(1)
.getMessage());
assertEquals(Level.INFO, logsList.get(1)
.getLevel());
}
}
JUnit断言听起来不太适合断言列表元素的某些特定属性。 像AssertJ或Hamcrest这样的Matcher/断言库似乎更好:
使用AssertJ，它将是:
import org.assertj.core.api.Assertions;
Assertions.assertThat(listAppender.list)
.extracting(ILoggingEvent::getMessage, ILoggingEvent::getLevel)
.containsExactly(Tuple.tuple("start", Level.INFO), Tuple.tuple("finish", Level.INFO));
对于Junit 5 (Jupiter)， Spring的OutputCaptureExtension非常有用。它从Spring Boot 2.2开始就可以使用，并且可以在Spring - Boot -test构件中使用。
示例(取自javadoc):
@ExtendWith(OutputCaptureExtension.class)
class MyTest {
@Test
void test(CapturedOutput output) {
System.out.println("ok");
assertThat(output).contains("ok");
System.err.println("error");
}
@AfterEach
void after(CapturedOutput output) {
assertThat(output.getOut()).contains("ok");
assertThat(output.getErr()).contains("error");
}
}
请注意，在Log4J 2中。X，公共接口org.apache.logging.log4j。Logger不包括setAppender()和removeAppender()方法。
但是，如果您没有做太花哨的事情，您应该能够将它强制转换为实现类org.apache.logging.log4j.core。记录器，它公开了这些方法。
这里有一个Mockito和AssertJ的例子:
// Import the implementation class rather than the API interface
import org.apache.logging.log4j.core.Logger;
// Cast logger to implementation class to get access to setAppender/removeAppender
Logger log = (Logger) LogManager.getLogger(MyClassUnderTest.class);
// Set up the mock appender, stubbing some methods Log4J needs internally
Appender appender = mock(Appender.class);
when(appender.getName()).thenReturn("Mock Appender");
when(appender.isStarted()).thenReturn(true);
log.addAppender(appender);
try {
new MyClassUnderTest().doSomethingThatShouldLogAnError();
} finally {
log.removeAppender(appender);
}
// Verify that we got an error with the expected message
ArgumentCaptor<LogEvent> logEventCaptor = ArgumentCaptor.forClass(LogEvent.class);
verify(appender).append(logEventCaptor.capture());
LogEvent logEvent = logEventCaptor.getValue();
assertThat(logEvent.getLevel()).isEqualTo(Level.ERROR);
assertThat(logEvent.getMessage().getFormattedMessage()).contains(expectedErrorMessage);
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。
