Add tests for `ContentSchema` class
user
```ruby
require "spec_helper"

RSpec.describe ContentSchema do
  describe '#frontend_schema' do
    it "it can link to GitHub" do
      schema = ContentSchema.new("generic").frontend_schema

      expect(schema.link_to_github).to eql('https://github.com/alphagov/govuk-content-schemas/blob/master/dist/formats/generic/frontend/schema.json')
    end

    it "it has a random example" do
      schema = ContentSchema.new("generic").frontend_schema

      expect(schema.random_example['content_id']).not_to be_nil
    end

    it "it has properties with inlined definitions" do
      schema = ContentSchema.new("generic").frontend_schema

      expect(schema.properties['base_path']["$ref"]).to eql(nil)
      expect(schema.properties['base_path']["type"]).to eql("string")
    end
  end

  describe '#publisher_content_schema' do
    it "it can link to GitHub" do
      schema = ContentSchema.new("generic").publisher_content_schema

      expect(schema.link_to_github).to eql('https://github.com/alphagov/govuk-content-schemas/blob/master/dist/formats/generic/publisher/schema.json')
    end

    it "it has a random example" do
      schema = ContentSchema.new("generic").publisher_content_schema

      expect(schema.random_example['base_path']).not_to be_nil
    end

    it "it has properties with inlined definitions" do
      schema = ContentSchema.new("generic").publisher_content_schema

      expect(schema.properties['base_path']["$ref"]).to eql(nil)
      expect(schema.properties['base_path']["type"]).to eql("string")
    end
  end

  describe '#publisher_links_schema' do
    it "it can link to GitHub" do
      schema = ContentSchema.new("generic").publisher_links_schema

      expect(schema.link_to_github).to eql('https://github.com/alphagov/govuk-content-schemas/blob/master/dist/formats/generic/publisher/links.json')
    end
  end
end
```
assistant