加入 invalid course 的 case

require "rails_helper"

describe "user create course", :type => :feature do
  scenario "valid" do
    course = build_stubbed(:course)

    course_form.create(course.title, course.description)

    expect(page).to have_text(course.title)
  end

+  scenario "invalid" do
+    course_form.create "", ""
+    expect(page).to have_text("Add a course")
+  end

  private

    def course_form
      sign_in
      home_page.go
      home_page.add_course
    end

    def home_page
      PageObjects::Pages::Home.new
    end
end