    @Test
    void add() {

        final YamlConfiguration configuration = new YamlConfiguration();
        final YamlConfigurationOptions options = new TestYamlConfigurationOptions(configuration);
        final KeyTree tree = new KeyTree(options);
        final String defaultnodekey = "defaultnodekey";
        final String nodewithcommentkey = "nodewithcommentkey";
        tree.add(defaultnodekey);
        tree.add(nodewithcommentkey);
        final KeyTree.Node defaultnode = tree.get(defaultnodekey);
        final KeyTree.Node nodewithcomment = tree.get(nodewithcommentkey);
        final String commentOfNodewithcomment = "Comment of nodewithcomment";
        final String sideCommentOfNodewithcomment = "Side comment of nodewithcomment";
        nodewithcomment.setComment(commentOfNodewithcomment);
        nodewithcomment.setSideComment(sideCommentOfNodewithcomment);

        MatcherAssert.assertThat(
            "The node has a root!",
            defaultnode.getIndentation(),
            new IsEqual<>(0)
        );
        MatcherAssert.assertThat(
            "The node's name is not correct!",
            defaultnode.getName(),
            new IsEqual<>(defaultnodekey)
        );
        MatcherAssert.assertThat(
            "There is a comment!",
            defaultnode.getComment(),
            new IsNull<>()
        );
        MatcherAssert.assertThat(
            "There is a side comment!",
            defaultnode.getSideComment(),
            new IsNull<>()
        );

        MatcherAssert.assertThat(
            "The node has a root!",
            nodewithcomment.getIndentation(),
            new IsEqual<>(0)
        );
        MatcherAssert.assertThat(
            "The node's name is not correct!",
            nodewithcomment.getName(),
            new IsEqual<>(nodewithcommentkey)
        );
        MatcherAssert.assertThat(
            "There is not a a comment!",
            nodewithcomment.getComment(),
            new IsEqual<>(commentOfNodewithcomment)
        );
        MatcherAssert.assertThat(
            "There is not a side comment!",
            nodewithcomment.getSideComment(),
            new IsEqual<>(sideCommentOfNodewithcomment)
        );
    }