How to set environment variable for logback custom property in JUnit test?

Question

In my application, JUnit test case is written with the help of spring configuration. I have Recently added some custom properties in my logback.xml file to store system logs with the help of SyslogAppneder as,

logback.xml (snippet)

<appender name="RSYSLOG" class="ch.qos.logback.classic.net.SyslogAppender">
    <syslogHost>${HOST}</syslogHost>
    <facility>${FACILITY}</facility>
    <port>${PORT}</port>
    <suffixPattern>%msg</suffixPattern>
</appender>

I can very well run my application by setting these properties in environment variable without JUnit test cases.

How can I set these properties to execute JUnit Test case in Jenkins or any CI system.