Test Results window showing 'Running' when AfterClass writes to the console

Reproduction scenario:
1. Create a new JAVA Gradle project in NB12
2. Create a new Test code as follows (using either JUnit 4 or TestNG 6+)

import org.junit.AfterClass;
import org.junit.Test;
public class ExampleTest {
  @AfterClass
  public static void cleanup() {
    // if you comment out the next line, the TestResults window will properly show the test results
    System.out.println("Cleaned");
  }
  @Test
  public void testSomeMethod() {
    System.out.println("Doing something.");
  }
}

3. Hit CTLR+F6 and check the the results in the `Test Results` window. It will still show 'Running' as opposed to the actual test result.
4. Comment out the line System.out.println("Cleaned"); and hit CTLR+F6 again and check the TestResults window.

Bug applies to NB11 and above. Tested on LINUX, JDK11 and JDK8. It does not matter, if the write to the console is directly, or through a logger.
Using a MAVEN project works just OK.