How to configure log4j.properties for SpringJUnit4ClassRunner?

Question

Suddenly this keeps happening during a JUnit test. Everything was working, I wrote some new tests and this error occured. If I revert it, it won\'t go away. Why is that?

Answer 1

The new tests you wrote (directly or indirectly) use classes that log using Log4j.

Log4J needs to be configured for this logging to work properly.

Put a log4j.properties (or log4j.xml) file in the root of your test classpath.

It should have some basic configuration such as

# Set root logger level to DEBUG and its only appender to A1.
log4j.rootLogger=DEBUG, A1

# A1 is set to be a ConsoleAppender.
log4j.appender.A1=org.apache.log4j.ConsoleAppender

# A1 uses PatternLayout.
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n

# An alternative logging format:
# log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1} - %m%n

An appender outputs to the console by default, but you can also explicitly set the target like this:

log4j.appender.A1.Target=System.out

This will redirect all output in a nice format to the console. More info can be found here in the Log4J manual,

Log4J Logging will then be properly configured and this warning will disappear.