Support multiple file upload with Firefox

lib/capybara/selenium/node.rb

@@ -279,10 +279,11 @@ private
 
   def set_file(value) # rubocop:disable Naming/AccessorMethodName
     path_names = value.to_s.empty? ? [] : value
-    if driver.chrome?
-      native.send_keys(Array(path_names).join("\n"))
+    if driver.marionette?
+      native.clear
+      Array(path_names).each { |p| native.send_keys(p) }
     else
-      native.send_keys(*path_names)
+      native.send_keys(Array(path_names).join("\n"))
     end
   end
 

lib/capybara/spec/session/attach_file_spec.rb

@@ -73,7 +73,6 @@ Capybara::SpecHelper.spec "#attach_file" do
     end
 
     it "should not break when using HTML5 multiple file input uploading multiple files" do
-      pending "Selenium is buggy on this, see http://code.google.com/p/selenium/issues/detail?id=2239" if @session.respond_to?(:mode) && @session.mode.to_s =~ /^selenium_(firefox|marionette)/
       @session.attach_file("Multiple Documents",
                            [@test_file_path, @another_test_file_path].map { |f| with_os_path_separators(f) })
       @session.click_button('Upload Multiple')
@@ -86,6 +85,16 @@ Capybara::SpecHelper.spec "#attach_file" do
       @session.click_button('Upload Empty Multiple')
       expect(@session).to have_content("Successfully ignored empty file field")
     end
+
+    it "should not append files to already attached" do
+      @session.attach_file "Multiple Documents", with_os_path_separators(@test_file_path)
+      @session.attach_file("Multiple Documents",
+                           [@test_file_path, @another_test_file_path].map { |f| with_os_path_separators(f) })
+      @session.click_button('Upload Multiple')
+      expect(@session.body).to include("2 | ") # number of files
+      expect(@session.body).to include(File.read(@test_file_path))
+      expect(@session.body).to include(File.read(@another_test_file_path))
+    end
   end
 
   context "with a locator that doesn't exist" do