Demonstration of TextArea's observable state inconsistency

TextAreaConsistency.java

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.IndexRange;
import javafx.scene.control.TextArea;
import javafx.stage.Stage;

public class TextAreaConsistency extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) {
        TextArea area = new TextArea();

        area.caretPositionProperty().addListener(obs -> checkConsistency(area));
        area.anchorProperty().addListener(obs -> checkConsistency(area));
        area.selectionProperty().addListener(obs -> checkConsistency(area));

        stage.setScene(new Scene(area));
        stage.show();
    }

    private static void checkConsistency(TextArea area) {
        IndexRange selection = area.getSelection();
        int caretPosition = area.getCaretPosition();
        int anchor = area.getAnchor();
        assert selection.equals(IndexRange.normalize(anchor, caretPosition));
    }
}

Run the above program and type a letter into the text area. Don't forget to enable assertions. Tested with JDK 8u20 b13.

Used as an example in How to ensure consistency of your observable state.