JDK-8214253, fix was made to correct the background color of JTooltip as tooltip was looking transparent instead of having black background. No automated test was written to verify the results. Current bug is to write the automated tests for the same.
JDK-8221781 was created to add automated tests for a number of fixes done related to gtk3. The current fix covers JTooltip widget from the widgets listed in JDK-8221781