Java Tester bugged on "Add Tags to a Course" code challenge under the "Java Data Structures" course.

If you're going through the Java Data Structures course, you come across the second code challenge under the "MVP" section named "Add Tags to a Course." The first task asks you to initialize the member set of tags in the constructor. The problem though is if you add another parameter for the constructor to accept a list or set of "tags" to initialize the set with, the Java Tester throws up an error because it's trying to use a single parameter. And if you try to initialize the set of "tags" without a parameter by simply using ".add()" to the set it will give you a null pointer exception. I've even tried method signatures and created a second constructor that accepts two, while leaving the first constructor alone, and the task will ask if I've initialized the set of "tags." I believe the Java Tester is not performing the correct tests or something is bugged with the code challenge and task.

package com.example.model;

import java.util.List;
import java.util.Set;
import java.util.HashSet;

public class Course {
  private String mTitle;
  private Set<String> mTags;

  public Course(String title, List<String> tags) {
    mTitle = title;
    // TODO: initialize the set mTags
    mTags = new HashSet<String>(tags);
  }

  public Course(String title) {
    mTitle = title;
    mTags.add("New Tag");
  }

  public void addTag(String tag) {
    // TODO: add the tag
  }

  public void addTags(List<String> tags) {
    // TODO: add all the tags passed in
  }

  public boolean hasTag(String tag) {
    // TODO: Return whether or not the tag has been added
    return false;
  }

  public String getTitle() {
    return mTitle;
  }

}