LoggerMatcher.java

// Copied from https://github.com/Mahoney/slf4j-test/issues/3 and slightly modified.

import org.hamcrest.BaseMatcher;
import org.hamcrest.Description;
import org.hamcrest.Matcher;
import org.slf4j.event.Level;
import org.slf4j.event.LoggingEvent;
import org.slf4j.helpers.MessageFormatter;

public class LoggerMatcher {
    public static Matcher<LoggingEvent> logWithLevelAndMessage(final Level level, final String substring) {
        return new BaseMatcher<LoggingEvent>() {
            @Override
            public boolean matches(Object item) {
                if (item instanceof LoggingEvent) {
                    final LoggingEvent le = (LoggingEvent) item;

                    return le.getLevel().equals(level) && getFormattedMessage(le).contains(substring);
                }

                return false;
            }

            @Override
            public void describeTo(Description description) {
                description
                        .appendText("LoggingEvent with level ")
                        .appendValue(level)
                        .appendText(" and a formatted message containing '")
                        .appendText(substring)
                        .appendText("'");
            }
        };
    }

    private static String getFormattedMessage(LoggingEvent event) {
        return MessageFormatter.arrayFormat(event.getMessage(), event.getArgumentArray()).getMessage();
    }
}