Ruby on Rails Coursera Class Bug in Tests

I'm currently taking Coursera's free Ruby on Rails Introduction class. I'm working on the third assignment which contains creating a People class where you have some functionality like a search function.

I'm getting a weird error when I run rspec with their designed unit tests. I'm 99% sure the error is lying in the unit tests. Specifically, before I've even touched any files, I'm getting the following error:

        raise <<-EOS
        #{description} accessed in #{article} #{hook_expression} hook at:
          #{CallerFilter.first_non_rspec_line}

        `let` and `subject` declarations are not intended to be called
        in #{article} #{hook_expression} hook, as they exist to define state that
        is reset between each example, while #{hook_expression} exists to
        #{hook_intention}.
        EOS

      RuntimeError:
        let declaration `class` accessed in an `after(:context)` hook at:
          /Users/<username>/.rvm/gems/ruby-2.4.0/gems/rspec-core-3.7.1/exe/rspec:4:in `<top (required)>'

        `let` and `subject` declarations are not intended to be called
        in an `after(:context)` hook, as they exist to define state that
        is reset between each example, while `after(:context)` exists to
        cleanup state that is shared across examples in an example group.

For starters, I don't totally understand the syntax they're using to describe talking about their tests. Secondly, here is the raw testing file that the author's of the Coursera class wrote:

require 'rspec'
require 'rspec/its'
require_relative '../module2_lesson3_formative.rb'

describe "lesson3" do

  context "check results" do
    p1 = Person.new("Ivana", "Trump")
    p2 = Person.new("Eric", "Trump")
    p3 = Person.new("Melania", "Trump")
    p4 = Person.new("Marla", "Maples")

    it "unexpected search result" do
      expect(Person.search("Trump").size).to be == 3
    end
  end

  context "check instance properties" do
    subject(:john) { Person.new("Chris", "Christie") }

    it "missing first_name" do
      is_expected.to respond_to(:first_name)
    end

    it "missing last_name" do
      is_expected.to respond_to(:last_name)
    end

  end

  context "check class properties" do
    subject(:class) { Person }

    it "missing search" do
      is_expected.to respond_to(:search)
    end
  end
end

I am hoping that someone can explain to me the debugging information when I run rspec. I'm using RSpec 3.7 which I'm guessing is the problem, as indicated that it might be a versioning upgrade thing here. That would also explain the fact that the class's authors didn't intentionally push up bad code. What is the best way for me to fix this and why are lines like this:

subject(:john) { Person.new("Chris", "Christie") }

in bad form? Thanks so much! Really appreciate your time :)