class ConfigNode {

    protected int getNodeDepth() {
        return parent != null ? parent.getNodeDepth() + 1 : -1; // Root node is -1
    }

}

class ConfigNodeTest {

    private static final String SIMPLE_STRING_NODE;
    private static final String STRING_NODE_WITH_QUOTES;
    private static final String STRING_NODE_WITH_DOUBLE_QUOTES;
    private static final String FIRST_LEVEL;
    private static final String SECOND_LEVEL;
    private static final String THIRD_LEVEL;
    private ConfigNode testTree;

    @Test
    void rootNodeReturnsDepthZero() {

        assertEquals(-1, testTree.getNodeDepth());
    }

}