Representing has_many :though with Factory Bot

Given the model set up like this:

class Course < ApplicationRecord
  belongs_to :faculty
  has_many :teachings
  has_many :faculty, through: :teachings

  validates :name, uniqueness: { scope: [:faculty_id, :period,
                                         :semester, :year] }
end

class Faculty < ApplicationRecord
  has_secure_password

  has_many :courses
  has_many :courses, :through => :teachings

  validates :email, { presence: true, uniqueness: true }
  validates :first_name, presence: true
  validates :last_name, presence: true
  validates :password, presence: true
end

I am trying to test the creation of course like so:

RSpec.describe Course, :type => :model do

  it "is valid with when period and faculty are unique" do
    course = create(:course)
    expect(course).to be_invalid
  end
end

I get the following error when I run the test:

1) Course is valid with when period and faculty are unique Failure/Error: course = create(:course)

 ActiveRecord::RecordInvalid:
   Validation failed: Faculty must exist

I have tried creating a faculty, and using that in the creation of the course, yet still know luck.

I have looked up how to deal with factory bot and relations and tried some of that, but I'm just too ignorant on testing to get it to work. I'm hoping to get some insight specific to my situation right now.