logback create a new log instance programmatically

Question

I am having a small query with LogBack in Java and i'm hoping someone on the forum might have the solution for me.

I am running some tests, I can run those tests in singles or multiples. When I am running them in multiples is where I get the issue. I want to log file to change depending on the name of the test case. For example when I run 10 tests and test 1 id 1, when that finishes and test 2 starts I want that to be reflected to the log file and I want a second log file to be created with id 2.

I hope that makes sense, and if you have any additional questions please don't hesitate to ask.

Thank you in advance.

Answer 1

You can use Logback's SiftingAppender.

<?xml version="1.0" encoding="UTF-8"?>
<configuration>

    <appender name="SIFTER" class="ch.qos.logback.classic.sift.SiftingAppender">
        <discriminator>
            <key>testName</key>
            <defaultValue>UNKNOWN</defaultValue>
        </discriminator>
        <sift>
            <appender name="FILE-${testName}" class="ch.qos.logback.core.FileAppender">
                <file>test-${testName}.log</file>
                <layout class="ch.qos.logback.classic.PatternLayout">
                    <pattern>...</pattern>
                </layout>
            </appender>
        </sift>
    </appender>

    <root level="ALL">
        <appender-ref ref="SIFTER" />
    </root>
</configuration>

The value of testName will be substituted into the log file name. You set testName via org.slf4j.MDC. For example;

String testName = "...";
MDC.put("testName", testName);

// run your test
// ...

// remove the test name from MDC ready for the next test to set its own name
MDC.remove("testName");

You could use JUnit4's TestName Rule to get the current test name and then put/remove in @Before, @After methods.