old_contents: describe("About Mutability", function() {
  
    it("should expect object properties to be public and mutable", function () {
      var aPerson = {firstname: "John", lastname: "Smith" };
      aPerson.firstname = "Alan";
      
      expect(aPerson.firstname).toBe(FILL_ME_IN);
    });
  
    it("should understand that constructed properties are public and mutable", function () {
      function Person(firstname, lastname)
      {
        this.firstname = firstname;
        this.lastname = lastname;
      }
      var aPerson = new Person ("John", "Smith");
      aPerson.firstname = "Alan";
      
      expect(aPerson.firstname).toBe(FILL_ME_IN);
    });
  
    it("should expect prototype properties to be public and mutable", function () {
      function Person(firstname, lastname)
      {
        this.firstname = firstname;
        this.lastname = lastname;
      }
      Person.prototype.getFullName = function () {
        return this.firstname + " " + this.lastname;
      };
      
      var aPerson = new Person ("John", "Smith");
      expect(aPerson.getFullName()).toBe(FILL_ME_IN);
      
      aPerson.getFullName = function () {
        return this.lastname + ", " + this.firstname;
      };
      
      expect(aPerson.getFullName()).toBe(FILL_ME_IN);
    });
  
    it("should know that variables inside a constructor and constructor args are private", function () {
      function Person(firstname, lastname)
      {
        var fullName = firstname + " " + lastname;
        
        this.getFirstName = function () { return firstname; };
        this.getLastName = function () { return lastname; };
        this.getFullName = function () { return fullName; };
      }
      var aPerson = new Person ("John", "Smith");
  
      aPerson.firstname = "Penny";
      aPerson.lastname = "Andrews";
      aPerson.fullName = "Penny Andrews";
      
      expect(aPerson.getFirstName()).toBe(FILL_ME_IN);
      expect(aPerson.getLastName()).toBe(FILL_ME_IN);
      expect(aPerson.getFullName()).toBe(FILL_ME_IN);
  
      aPerson.getFullName = function () {
        return aPerson.lastname + ", " + aPerson.firstname;
      };
      
      expect(aPerson.getFullName()).toBe(FILL_ME_IN);
    });
  
  });
  
new_contents: describe("About Mutability", function() {
  
    it("should expect object properties to be public and mutable", function () {
      var aPerson = {firstname: "John", lastname: "Smith" };
      aPerson.firstname = "Alan";
      
      expect(aPerson.firstname).toBe("Alan");
    });
  
    it("should understand that constructed properties are public and mutable", function () {
      function Person(firstname, lastname)
      {
        this.firstname = firstname;
        this.lastname = lastname;
      }
      var aPerson = new Person ("John", "Smith");
      aPerson.firstname = "Alan";
      
      expect(aPerson.firstname).toBe("Alan");
    });
  
    it("should expect prototype properties to be public and mutable", function () {
      function Person(firstname, lastname)
      {
        this.firstname = firstname;
        this.lastname = lastname;
      }
      Person.prototype.getFullName = function () {
        return this.firstname + " " + this.lastname;
      };
      
      var aPerson = new Person ("John", "Smith");
      expect(aPerson.getFullName()).toBe("John Smith");
      
      aPerson.getFullName = function () {
        return this.lastname + ", " + this.firstname;
      };
      
      expect(aPerson.getFullName()).toBe("Smith, John");
    });
  
    it("should know that variables inside a constructor and constructor args are private", function () {
      function Person(firstname, lastname)
      {
        var fullName = firstname + " " + lastname;
        
        this.getFirstName = function () { return firstname; };
        this.getLastName = function () { return lastname; };
        this.getFullName = function () { return fullName; };
      }
      var aPerson = new Person ("John", "Smith");
  
      aPerson.firstname = "Penny";
      aPerson.lastname = "Andrews";
      aPerson.fullName = "Penny Andrews";
      
      expect(aPerson.getFirstName()).toBe("John");
      expect(aPerson.getLastName()).toBe("Smith");
      expect(aPerson.getFullName()).toBe("John Smith");
  
      aPerson.getFullName = function () {
        return aPerson.lastname + ", " + aPerson.firstname;
      };
      
      expect(aPerson.getFullName()).toBe("Andrews, Penny");
    });
  
  });
  
subject: add completed mutability code