Fix #tables deprecation in Rails 5.0 and keep compatibility with Rails 4.x

lib/shoulda/matchers/active_record/association_matchers/join_table_matcher.rb

@@ -38,7 +38,7 @@ module Shoulda
           end
 
           def join_table_exists?
-            if connection.tables.include?(join_table_name)
+            if RailsShim.tables_and_views(connection).include?(join_table_name)
               true
             else
               @failure_message = missing_table_message

lib/shoulda/matchers/rails_shim.rb

@@ -55,6 +55,14 @@ module Shoulda
         I18n.translate(primary_translation_key, translate_options)
       end
 
+      def self.tables_and_views(connection)
+        if active_record_major_version >= 5
+          connection.data_sources
+        else
+          connection.tables
+        end
+      end
+
       def self.active_record_major_version
         ::ActiveRecord::VERSION::MAJOR
       end