function assertTreeValues(tree, values) {
    const treeValues = [...tree.values()];
    assert.deepStrictEqual(treeValues, values);
}
Check that the contents of the tree match the values of the array.
@param {BinarySearchTree} tree The tree to check 
@param {Array} values An array of values that should match.
@throws {AssertionError} If the values in the tree don't match the
     values in the array.