Support enum attributes on validate_absence_of

lib/shoulda/matchers/active_model/validate_absence_of_matcher.rb

@@ -109,6 +109,8 @@ def value
             end
           elsif array_column?
             ['an arbitary value']
+          elsif enum_column?
+            enum_values.first
           else
             case column_type
             when :integer, :float then 1
@@ -145,6 +147,15 @@ def array_column?
             @subject.class.columns_hash[@attribute.to_s].respond_to?(:array) &&
             @subject.class.columns_hash[@attribute.to_s].array
         end
+
+        def enum_column?
+          @subject.class.respond_to?(:defined_enums) &&
+            @subject.class.defined_enums.key?(@attribute.to_s)
+        end
+
+        def enum_values
+          @subject.class.defined_enums[@attribute.to_s].values
+        end
       end
     end
   end

spec/unit/shoulda/matchers/active_model/validate_absence_of_matcher_spec.rb

@@ -91,6 +91,16 @@ def self.available_column_types
         end
       end
 
+      context 'when the column backing the attribute is an enum' do
+        it 'still works' do
+          record = active_model_validating_absence_of(:attr) do
+            enum attr: %w[one two three]
+          end
+
+          expect(record).to validate_absence_of(:attr)
+        end
+      end
+
       context 'when used in the negative' do
         it 'fails' do
           assertion = lambda do
@@ -295,9 +305,13 @@ def active_model_with(attr, &block)
       define_active_model_class('Example', accessors: [attr], &block).new
     end
 
-    def active_model_validating_absence_of(attr)
+    def active_model_validating_absence_of(attr, &block)
       active_model_with(attr) do
         validates_absence_of attr
+
+        if block
+          class_eval(&block)
+        end
       end
     end