assertj-logging - assertj assertions for logging

assertj-logging's intention is to provide an easy way to unit test expected logging for different logging implementations with JUnit and AssertJ.

Starting with version 0.5.0 a JUnit 5 extension is provided and JUnit 4 is no longer supported.

Versions up to 0.4.X provide a JUnit 4 @Rule.

It currently supports

• log4j 2.x: assertj-logging-log4j
• logback: assertj-logging-logback

Contents

• Configuration
• How it works
• Usage

Configuration

Gradle

build.gradle

dependencies {
    testImplementation 'de.neuland-bfi:assertj-logging-log4j:0.4.0'
}

Maven

pom.xml

<dependency>
    <groupId>de.neuland-bfi</groupId>
    <artifactId>assertj-logging-log4j</artifactId>
    <version>0.5.0</version>
    <scope>test</scope>
</dependency>

How it works

assert-logging provides a JUnit rule that adds an appender to capture log messages to the logger of the logging source (the class emitting log messages).

After execution of the code under test this rule can be fed to a set of AssertJ assertions to verify that the expected logging was emitted.

Usage

JUnit 5

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.RegisterExtension;

import de.neuland.assertj.logging.ExpectedLogging;

import static de.neuland.assertj.logging.ExpectedLoggingAssertions.assertThat;

public class LoggingSourceTest {
    @RegisterExtension
    private final ExpectedLogging logging = ExpectedLogging.forSource(LoggingSource.class);

    @Test
    void shouldCaptureLogging() {
        // given
        String expectedMessage = "Error Message";

        // when
        new LoggingSource().doSomethingThatLogsErrorMessage();

        // then
        assertThat(logging).hasErrorMessage(expectedMessage);
    }
}

JUnit 4

import org.junit.Rule;
import org.junit.Test;

import de.neuland.assertj.logging.ExpectedLogging;

import static de.neuland.assertj.logging.ExpectedLoggingAssertions.assertThat;

public class LoggingSourceTest {
    @Rule
    public ExpectedLogging logging = ExpectedLogging.forSource(LoggingSource.class);

    @Test
    public void shouldCaptureLogging() {
        // given
        String expectedMessage = "Error Message";

        // when
        new LoggingSource().doSomethingThatLogsErrorMessage();

        // then
        assertThat(logging).hasErrorMessage(expectedMessage);
    }
}

Supported Log Levels

We consider ERROR, WARNING and INFO to be the test-worthy log levels.

Thus, assertj-logging provides assertions for these log levels.

Assertions

The following assertions are available:

assertThat(logging).hasErrorMessage(String message);
assertThat(logging).hasNoErrorMessage();
assertThat(logging).hasErrorMessage(String message, Throwable throwable);
assertThat(logging).hasErrorMessageMatching(String regex);
assertThat(logging).hasErrorMessageMatching(String regex, Throwable throwable);

assertThat(logging).hasWarningMessage(String message);
assertThat(logging).hasNoWarningMessage();
assertThat(logging).hasWarningMessage(String message, Throwable throwable);
assertThat(logging).hasWarningMessageMatching(String regex);
assertThat(logging).hasWarningMessageMatching(String regex, Throwable throwable);

assertThat(logging).hasInfoMessage(String message);
assertThat(logging).hasNoInfoMessage();
assertThat(logging).hasInfoMessageMatching(String regex);

All assertions from AssertJ's ListAssert are available as well, e.g.

assertThat(logging).isEmpty();