Fixed specs

lib/spectre/searchable.rb

@@ -3,7 +3,7 @@
 module Spectre
   module Searchable
     def self.included(base)
-      unless base.ancestors.include?(Mongoid::Document)
+      unless base.ancestors.map(&:to_s).include?('Mongoid::Document')
         raise "Spectre::Searchable can only be included in Mongoid models. The class #{base.name} does not appear to be a Mongoid model."
       end
 

spec/support/mongoid/document.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+module Mongoid
+  module Document; end
+end

spec/support/test_model.rb

@@ -1,9 +1,11 @@
 # frozen_string_literal: true
 
 require 'spectre'
+require_relative 'mongoid/document'
 
 class TestModel
   include Spectre
+  include Mongoid::Document
 
   spectre :embeddable, :searchable