Find the Minimum and Maximum Height of a Binary Search Tree(problem in test cases)

Tell us what’s happening:
There is problem in test case. My code is passed the test case, but actually on my system I chacked with tree example, it throw an error. So, I think there is problem in test cases.

Your code so far


var displayTree = tree => console.log(JSON.stringify(tree, null, 2));
function Node(value) {
this.value = value;
this.left = null;
this.right = null;
}
function BinarySearchTree() {
this.root = null;
// change code below this line

this.findMaxHeight=function(){
  if(this.root===null){
    return -1;
  }
  else{
    let ans=findMax(this.root);
    return ans-1; //add root also
  }
}
function findMax(tree){
    let lans=0;
    let rans=0;
    if(tree.left!==null){
      lans=1;
      lans+=findMax(tree.left);
    }
    else if(tree.right!==null){
      rans=1;
      rans+=findMax(tree.left);
    }
    else{
      return 1;
    }
    if(lans>rans){
      return lans;
    }
    else{
      return rans;
    }
}

this.findMinHeight=function(){
  //if tree is empty
  if(this.root===null){
    return -1;
  }
  else{
    let ans=findMin(this.root);
    return ans+1;
  }
}
function findMin(tree){
    let lans=0;
    let rans=0;
    if(tree.left!==null){
      lans+=findMin(tree.left);
    }
    else if(tree.right!==null){
      rans+=findMin(tree.left);
    }
    else{
      return 1;
    }
    if(lans<rans){
      return lans;
    }
    else{
      return rans;
    }
  }

// change code above this line
}

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Challenge: Find the Minimum and Maximum Height of a Binary Search Tree

Link to the challenge:
https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/find-the-minimum-and-maximum-height-of-a-binary-search-tree