For learning purpose will be good to add constructors to commented class TreeNode like this:
public static class TreeNode {
public int value;
public TreeNode left;
public TreeNode right;

    public TreeNode(int value) {
        this.value = value;
        this.left = this.right = null;
    }
    public TreeNode(int value, TreeNode left, TreeNode right) {
        this.value = value;
        this.left = left;
        this.right = right;
    }

}

JavaScript translation

Java fork Fixing test issue

the sample test should be present in the full test suite, in Java

no random tests in c#

it is not said if the tree should be inverted in place or not. Hence, currently, all solutions doing it in place while this is not explicitly allowed shouldn't pass

Added proper namespacing and class definitions to setup.

I think alle problems are fixed.

Fixed and closed.

Fixed and closed.

Fixed -> Issue closed

So now the issue is closed.