Question

In my app, I have the following code:

File.open "filename", "w" do |file|
  file.write("text")
end

I want to test this code via RSpec. What are the best practices for doing this?

Answer 1

I would suggest using StringIO for this and making sure your SUT accepts a stream to write to instead of a filename. That way, different files or outputs can be used (more reusable), including the string IO (good for testing)

So in your test code (assuming your SUT instance is sutObject and the serializer is named writeStuffTo:

testIO = StringIO.new
sutObject.writeStuffTo testIO 
testIO.string.should == "Hello, world!"

String IO behaves like an open file. So if the code already can work with a File object, it will work with StringIO.