另一个值得提及的想法是创建一个CDI生成器来注入记录器，这样模拟就变得容易了，尽管这是一个较老的主题。(而且它还提供了不必再声明“整个logger语句”的优势，但这已经跑题了)

例子:

创建要注入的记录器:

public class CdiResources {
  @Produces @LoggerType
  public Logger createLogger(final InjectionPoint ip) {
      return Logger.getLogger(ip.getMember().getDeclaringClass());
  }
}

限定符:

@Qualifier
@Retention(RetentionPolicy.RUNTIME)
@Target({TYPE, METHOD, FIELD, PARAMETER})
public @interface LoggerType {
}

在生产代码中使用记录器:

public class ProductionCode {
    @Inject
    @LoggerType
    private Logger logger;

    public void logSomething() {
        logger.info("something");
    }
}

在测试代码中测试记录器(给出一个easyMock示例):

@TestSubject
private ProductionCode productionCode = new ProductionCode();

@Mock
private Logger logger;

@Test
public void testTheLogger() {
   logger.info("something");
   replayAll();
   productionCode.logSomething();
}

简单的方法

  @ExtendWith(OutputCaptureExtension.class)
  class MyTestClass { 
    
          @Test
          void my_test_method(CapturedOutput output) {
               assertThat(output).contains("my test log.");
          }
  }

Here is the sample code to mock log, irrespective of the version used for junit or sping, springboot.

import ch.qos.logback.classic.spi.LoggingEvent;
import ch.qos.logback.core.Appender;
import org.mockito.ArgumentMatcher;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.junit.Test;

import static org.mockito.Matchers.argThat;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;

public class MyTest {
  private static Logger logger = LoggerFactory.getLogger(MyTest.class);

    @Test
    public void testSomething() {
    ch.qos.logback.classic.Logger root = (ch.qos.logback.classic.Logger) LoggerFactory.getLogger(ch.qos.logback.classic.Logger.ROOT_LOGGER_NAME);
    final Appender mockAppender = mock(Appender.class);
    when(mockAppender.getName()).thenReturn("MOCK");
    root.addAppender(mockAppender);

    //... do whatever you need to trigger the log

    verify(mockAppender).doAppend(argThat(new ArgumentMatcher() {
      @Override
      public boolean matches(final Object argument) {
        return ((LoggingEvent)argument).getFormattedMessage().contains("Hey this is the message I want to see");
      }
    }));
  }
}

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");
    }
}

如果您正在使用log4j2，来自https://www.dontpanicblog.co.uk/2018/04/29/test-log4j2-with-junit/的解决方案允许我断言消息已被记录。

解决方案是这样的:

Define a log4j appender as an ExternalResource rule public class LogAppenderResource extends ExternalResource { private static final String APPENDER_NAME = "log4jRuleAppender"; /** * Logged messages contains level and message only. * This allows us to test that level and message are set. */ private static final String PATTERN = "%-5level %msg"; private Logger logger; private Appender appender; private final CharArrayWriter outContent = new CharArrayWriter(); public LogAppenderResource(org.apache.logging.log4j.Logger logger) { this.logger = (org.apache.logging.log4j.core.Logger)logger; } @Override protected void before() { StringLayout layout = PatternLayout.newBuilder().withPattern(PATTERN).build(); appender = WriterAppender.newBuilder() .setTarget(outContent) .setLayout(layout) .setName(APPENDER_NAME).build(); appender.start(); logger.addAppender(appender); } @Override protected void after() { logger.removeAppender(appender); } public String getOutput() { return outContent.toString(); } } Define a test that use your ExternalResource rule public class LoggingTextListenerTest { @Rule public LogAppenderResource appender = new LogAppenderResource(LogManager.getLogger(LoggingTextListener.class)); private LoggingTextListener listener = new LoggingTextListener(); // Class under test @Test public void startedEvent_isLogged() { listener.started(); assertThat(appender.getOutput(), containsString("started")); } }

不要忘记将log4j2.xml作为src/test/resources的一部分

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