import org.antlr.runtime.tree.TreeVisitor;
import org.antlr.runtime.tree.TreeVisitorAction;
import org.antlr.v4.parse.GrammarASTAdaptor;
import org.antlr.v4.tool.ast.GrammarAST;

public class Grammarin {
    public void setGrammarPtr(final org.antlr.v4.tool.Grammar g, GrammarAST tree) {
        if (tree != null) {
            TreeVisitor v = new TreeVisitor(new GrammarASTAdaptor());
            v.visit(tree, new TreeVisitorAction() {
                public Object pre(Object t) {
                    ((GrammarAST) t).g = g;
                    return t;
                }

                public Object post(Object t) {
                    return t;
                }
            });
        }
    }
}

    @Test
    @DisplayName("setGrammarPtr: -> tree != null : True")
    public void testSetGrammarPtr_TreeNotEqualsNull_2() throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
        Grammarin grammarin = new Grammarin();
        GrammarRootAST tree = new GrammarRootAST(null);
        tree.token = null;
        Class baseTreeClazz = Class.forName("org.antlr.runtime.tree.BaseTree");
        Field childrenField = baseTreeClazz.getDeclaredField("children");
        childrenField.setAccessible(true);
        childrenField.get(tree) = new ArrayList();

        grammarin.setGrammarPtr(null, tree);
    }