Log4jExecutorTest.kt

import io.mockk.*
import org.apache.logging.log4j.ThreadContext
import org.junit.Test

class Log4jExecutorTest {
    class MyLog4jExecutor : Log4jExecutor() {
        fun runBefore(t: Thread?, r: Runnable?) = beforeExecute(t, r)
    }

    @Test
    fun beforeExecute() {
        val executor = spyk<MyLog4jExecutor>(recordPrivateCalls = true)
        val t = mockk<Thread>(relaxed = true)
        val r = mockk<Runnable>(relaxed = true)
        staticMockk(ThreadContext::class.java.name).use {
            executor.runBefore(t,r)
            verify { ThreadContext.putAll(any()) }
        }

    }
}