Log4j2 Mock Appender

Question

I have a class in which I take all of my Properties, and hide their passwords before logging.

@Override
public void afterPropertiesSet() throws Exception {
    Properties loadedProperties = this.mergeProperties();
    loadedProperties.entrySet().stream().forEach(singleProperty -> {
        String key = singleProperty.getKey().toString();
        String value = HIDDEN_VALUE;

        if (!Arrays.stream(PASSWORD_PATTERNS).anyMatch(pattern -> key.toLowerCase().contains(pattern))) {
            value = singleProperty.getValue().toString();                  
        }

        logger.info("LoadedProperty: "+ key +"=" + value);
    });
}

I have migrated to log4j2 and would like to test this class, checking the output of log4j2. It currently uses log4j and works, however when I migrated to log4j2, I get

Wanted but not invoked: mockAppender.append(); -> at com.comp.spmConf.ExceptionLoggerTest.verifyErrorMessages(ExceptionLoggerTest.java:87)

However, there were other interactions with this mock: mockAppender.getName(); -> at org.apache.logging.log4j.core.config.AbstractConfiguration.addLoggerAppender(AbstractConfiguration.java:675)

mockAppender.getName(); -> at org.apache.logging.log4j.core.config.AppenderControl.(AppenderControl.java:51)

Here is my log4j1 test class:

import org.apache.log4j.Appender;
import org.apache.log4j.LogManager;
import org.apache.log4j.spi.LoggingEvent;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.ArgumentCaptor;
import org.mockito.Captor;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.runners.MockitoJUnitRunner;

import java.util.Properties;

@RunWith(MockitoJUnitRunner.class)
public class SpmPropertyTracerTest {

@Mock
private Appender appenderMock;

@Captor
private ArgumentCaptor captorLoggingEvent;

private SpmPropertyTracer tracer;

@Before
public void setup() {
    LogManager.getRootLogger().addAppender(appenderMock);
    tracer = new SpmPropertyTracer();
}

@After
public void teardown() {
    LogManager.getRootLogger().removeAppender(appenderMock);
}

@Test
public void printPropertiesTest() throws Exception{
    String key1 = "Foo";
    String val1 = "True";
    Properties properties = new Properties();
    properties.setProperty(key1, val1);
    tracer.setProperties(properties);
    String expectedString = String.format("LoadedProperty: %s=%s", key1, val1);
    tracer.afterPropertiesSet();
    Mockito.verify(appenderMock).doAppend((LoggingEvent)captorLoggingEvent.capture());
    LoggingEvent loggingEvent = (LoggingEvent) captorLoggingEvent.getValue();
    assert expectedString.equals(loggingEvent.getRenderedMessage());
}

}

And here is my log4j2 test class, am I doing something wrong in the log4j to log4j2 migration?

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.Logger;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.ArgumentCaptor;
import org.mockito.Captor;
import org.mockito.Mock;
import org.mockito.runners.MockitoJUnitRunner;

import java.util.Properties;

import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.*;



@RunWith(MockitoJUnitRunner.class)
public class TestClass {
@Mock
private Appender mockAppender;
@Captor
private ArgumentCaptor<LogEvent> captorLoggingEvent;

private SpmPropertyTracer tracer;

private Logger logger;

private LogEvent logEvent;

@Before
public void setup() {
    // prepare the appender so Log4j likes it
    when(mockAppender.getName()).thenReturn("MockAppender");
    when(mockAppender.isStarted()).thenReturn(true);
    when(mockAppender.isStopped()).thenReturn(false);

    logger = (Logger)LogManager.getLogger(SpmPropertyTracer.class);
    logger.addAppender(mockAppender);
    logger.setLevel(Level.INFO);

    tracer = new SpmPropertyTracer();
}

@After
public void tearDown() {
    // the appender we added will sit in the singleton logger forever
    // slowing future things down - so remove it
    logger.removeAppender(mockAppender);
}

@Test
public void loggingIsCaptured() throws Exception {
    String key1 = "Foo";
    String val1 = "True";
    Properties properties = new Properties();
    properties.setProperty(key1, val1);
    tracer.setProperties(properties);
    String expectedString = String.format("LoadedProperasdfty: %s=%s", key1, val1);
    tracer.afterPropertiesSet();
    verifyErrorMessages(expectedString);
}


// handy function to inspect the messages sent to the logger
private void verifyErrorMessages(String ... messages) {
    verify(mockAppender, times(messages.length)).append((LogEvent)captorLoggingEvent.capture());

    int i=0;
    for(LogEvent loggingEvent:captorLoggingEvent.getAllValues()) {
        assertEquals(messages[i++], loggingEvent.getMessage().getFormattedMessage());
    }
}

Answer 1

The parent project was brining in a log4j dependency, thus slf4j was binding with log4j and not log4j2 and that is why the append method was not invoked. Removing that dependency fixed my errors.