close #98 by adding respond_to?

lib/active_interaction/modules/method_missing.rb

@@ -3,18 +3,26 @@
 module ActiveInteraction
   # @private
   module MethodMissing
+    def respond_to?(slug, include_all = false)
+      !!filter(slug) || super
+    end
+
     def method_missing(slug, *args, &block)
-      begin
-        klass = Filter.factory(slug)
-      rescue MissingFilterError
-        super
-      end
+      super unless (klass = filter(slug))
 
       options = args.last.is_a?(Hash) ? args.pop : {}
 
       yield(klass, args, options) if block_given?
 
       self
     end
+
+    private
+
+    def filter(slug)
+      Filter.factory(slug)
+    rescue MissingFilterError
+      nil
+    end
   end
 end

spec/active_interaction/modules/method_missing_spec.rb

@@ -6,6 +6,24 @@
   let(:klass) { Class.new { include ActiveInteraction::MethodMissing } }
   subject(:instance) { klass.new }
 
+  describe '#respond_to?(slug, include_all = false)' do
+    context 'with invalid slug' do
+      let(:slug) { :slug }
+
+      it 'returns false' do
+        expect(instance.respond_to?(slug)).to be_false
+      end
+    end
+
+    context 'with valid slug' do
+      let(:slug) { :boolean }
+
+      it 'returns true' do
+        expect(instance.respond_to?(slug)).to be_true
+      end
+    end
+  end
+
   describe '#method_missing' do
     context 'with invalid slug' do
       let(:slug) { :slug }