Match only projects that have all of the given project_types

gistfile1.rb

class Project < ActiveRecord::Base
  has_and_belongs_to_many :project_types

  scope :has_any_project_types, ->(*project_types) do
    joins(:project_types).
    where("project_types.id IN (?)", project_types)
  end

  scope :has_all_project_types, ->(*project_types) do
    joins(:project_types).
    where("project_types.id IN (?)", project_types).
    group("projects.id").
    having("count(*)=?", project_types.length)
  end
end

#Should get list of projects having any of the listed project_types
Project.has_any_project_types(4,6).all #Works as Expected

#Should get list of projects having all of the listed project_types
Project.has_all_project_types(4,6).all #Does not work as expected, does work as has_any_project_types.