Replace Field#included? with Field#excluded?.

lib/active_model/serializer/associations.rb

@@ -88,7 +88,7 @@ module ActiveModel
 
         Enumerator.new do |y|
           self.class._reflections.each do |reflection|
-            next unless reflection.included?(self)
+            next if reflection.excluded?(self)
             key = reflection.options.fetch(:key, reflection.name)
             next unless include_tree.key?(key)
             y.yield reflection.build_association(self, instance_options)

lib/active_model/serializer/attributes.rb

@@ -17,7 +17,7 @@ module ActiveModel
         def attributes(requested_attrs = nil, reload = false)
           @attributes = nil if reload
           @attributes ||= self.class._attributes_data.each_with_object({}) do |(key, attr), hash|
-            next unless attr.included?(self)
+            next if attr.excluded?(self)
             next unless requested_attrs.nil? || requested_attrs.include?(key)
             hash[key] = attr.value(self)
           end

lib/active_model/serializer/field.rb

@@ -24,14 +24,14 @@ module ActiveModel
       #
       # @api private
       #
-      def included?(serializer)
+      def excluded?(serializer)
         case condition_type
         when :if
-          serializer.public_send(condition)
-        when :unless
           !serializer.public_send(condition)
+        when :unless
+          serializer.public_send(condition)
         else
-          true
+          false
         end
       end