Unsure of how to find JOptionPanes

Hi,

I'm unsure of how to set up a project built in JOptionPane - I have used reflective elements before, however, the issue lies in the fact that the program I'm testing requires certain actions to take place between frames (for example, hit the OK button on a JOptionPane before doing the next test). I know this is generally a broad question, but how would I go about doing this? Also, on a different note, I'm currently getting this error

/Library/Java/JavaVirtualMachines/jdk-12.0.1.jdk/Contents/Home/bin/java -ea -Didea.test.cyclic.buffer.size=1048576 "-javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=56676:/Applications/IntelliJ IDEA.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath "/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar:/Applications/IntelliJ IDEA.app/Contents/plugins/junit/lib/junit-rt.jar:/Applications/IntelliJ IDEA.app/Contents/plugins/junit/lib/junit5-rt.jar:/Users/kedarabhyankar/Documents/CS Development/180 F19/SimpleGUIF19Lab/out/production/SimpleGUIF19Lab:/Library/Java/JavaVirtualMachines/libs/jemmy-2.3.0.0.jar:/Library/Java/JavaVirtualMachines/libs/remotecontent.jar:/Library/Java/JavaVirtualMachines/libs/hamcrest-all-1.3.jar:/Library/Java/JavaVirtualMachines/libs/assertj-swing-3.9.2.jar:/Library/Java/JavaVirtualMachines/libs/assertj-core-3.12.2.jar:/Library/Java/JavaVirtualMachines/libs/assertj-swing-junit-3.9.2.jar" com.intellij.rt.execution.junit.JUnitStarter -ideVersion5 -junit4 HackathonSignupFormTest
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.assertj.swing.dependency.fest_reflect.util.Accessibles$SetAccessibleAction (file:/Library/Java/JavaVirtualMachines/libs/assertj-swing-3.9.2.jar) to method javax.swing.SwingUtilities.appContextGet(java.lang.Object)
WARNING: Please consider reporting this to the maintainers of org.assertj.swing.dependency.fest_reflect.util.Accessibles$SetAccessibleAction
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

upon running of a test, and I'm unsure of what this means. My test simply runs the main code via
application(ApplicationName.class).start();

and then runs the tests accordingly.

Any help would be appreciated. Thanks!