```ruby
require 'test_helper'

class CategoryRelationshipTest < ActiveSupport::TestCase
  # test "the truth" do
  #   assert true
  # end
end
```

Add test for CategoryRelationship model
user
```ruby
require 'test_helper'

class CategoryRelationshipTest < ActiveSupport::TestCase
  test "CategoryRelationship without child_id should not be valid" do
    assert_not CategoryRelationship.new(child_id: nil).valid?
  end
end
```
assistant