add #form? and #xfa_form? methods to CombinePDF::PDF

lib/combine_pdf/pdf_public.rb

@@ -157,6 +157,14 @@ def clear_forms_data
       @forms_data.nil? || @forms_data.clear
     end
 
+    def form?
+      !@forms_data.nil?
+    end
+
+    def xfa_form?
+      form? && !@forms_data.dig(:referenced_object, :XFA).nil?
+    end
+
     # Save the PDF to file.
     #
     # file_name:: is a string or path object for the output.

test/combine_pdf/pdf_test.rb

@@ -0,0 +1,21 @@
+require 'bundler/setup'
+require 'minitest/autorun'
+require 'combine_pdf'
+
+describe CombinePDF::PDF do
+  subject { CombinePDF.load("test/fixtures/files/#{file}") }
+
+  describe 'AcroForm documents' do
+    let(:file) { 'acro_form.pdf' }
+
+    it('knows that it is an acro form') { assert(subject.form? == true) }
+    it('knows that it is NOT a dynamic XFA form') { assert(subject.xfa_form? == false) }
+  end
+
+  describe 'dynamic xfa documents' do
+    let(:file) { 'xfa_form.pdf' }
+
+    it('knows that it is an acro form') { assert(subject.form? == true) }
+    it('knows that it is IS a dynamic XFA form') { assert(subject.xfa_form? == true) }
+  end
+end