This is a new test provided with a fix to JDK-8146321 : it seems not working with GTK Look and Feel (means, on X11).

Error parsing gtk-icon-sizes string: ''
java.lang.IllegalArgumentException: Rectangle width and height must be > 0
at java.awt.Robot.checkValidRect(Robot.java:453)
at java.awt.Robot.createScreenCapture(Robot.java:410)
at JInternalFrameIconTest.getImageIconBufferedImage(JInternalFrameIconTest.java:186)
at JInternalFrameIconTest.executeCase(JInternalFrameIconTest.java:74)
at JInternalFrameIconTest.main(JInternalFrameIconTest.java:65)