Accept mode as argument in `file_write' action

spec/producer/core/remote/fs_spec.rb

@@ -126,7 +126,7 @@ module Producer::Core
         let(:content) { 'some_content' }
 
         it 'opens the file' do
-          expect(sftp_file).to receive(:open).with(path, 'w')
+          expect(sftp_file).to receive(:open).with(path, 'w', anything)
           fs.file_write path, content
         end
 
@@ -137,6 +137,11 @@ module Producer::Core
           end
           fs.file_write path, content
         end
+
+        it 'accepts an optional mode argument' do
+          expect(sftp_file).to receive(:open).with(anything, anything, 0600)
+          fs.file_write path, content, 0600
+        end
       end
     end
   end