Testing Logback Logger

XTest.java

Solution without PowerMock
--

    import ch.qos.logback.classic.*;
    import ch.qos.logback.classic.spi.LoggingEvent;
    import ch.qos.logback.core.Appender;
    import org.junit.*;
    import org.junit.runner.RunWith;
    import org.mockito.*;
    import org.mockito.runners.MockitoJUnitRunner;
    import org.slf4j.LoggerFactory;
    
    import static org.mockito.Matchers.argThat;
    import static org.mockito.Mockito.*;
    
    @RunWith(MockitoJUnitRunner.class)
    public class XTest {
    
        @Mock
        Appender mockAppender;
    
        X x = new X();
    
        @Before
        public void setUp() throws Exception {
            Logger root = (Logger) LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME);
            root.addAppender(mockAppender);
        }
    
        @Test
        public void whenFirstCaseErrorLogged() throws Exception {
            x.execute(true);
            thenLogged(Level.ERROR, "rumpampam");
        }
    
        @Test
        public void whenSecondCaseErrorLogged() throws Exception {
            x.execute(false);
            thenLogged(Level.ERROR, "latida");
        }
    
        private void thenLogged(Level level, String message) {
            verify(mockAppender).doAppend(argThat(hasLogged(level, message)));
        }
    
        private ArgumentMatcher hasLogged(final Level level, final String message) {
            return new ArgumentMatcher() {
                @Override
                public boolean matches(final Object argument) {
                    LoggingEvent loggingEvent = (LoggingEvent) argument;
                    return loggingEvent.getLevel().equals(level) &&
                            loggingEvent.getFormattedMessage().contains(message);
                }
            };
        }
    }

Solution based on excellent post [Functional testing : Asserting that a line was logged by Logback](http://jsoftbiz.wordpress.com/2011/11/29/unit-testing-asserting-that-a-line-was-logged-by-logback/)