How do I stub things in MiniTest?

Question

Within my test I want to stub a canned response for any instance of a class.

It might look like something like:

Book.stubs(:title).any_instance().ret         


        

Answer 1

You can always create a module in your test code, and use include or extend to monkey-patch classes or objects with it. eg (in book_test.rb)

module BookStub
  def title
     "War and Peace"
  end
end

Now you can use it in your tests

describe 'Book' do
  #change title for all books
  before do
    Book.include BookStub
  end
end

 #or use it in an individual instance
 it 'must be War and Peace' do
   b=Book.new
   b.extend BookStub
   b.title.must_equal 'War and Peace'
 end

This allows you to put together more complex behaviours than a simple stub might allow

Answer 2

You cannot stub all instances of a class, but you can stub any instance method of a given object like this:

require "minitest/mock"

book = Book.new
book.stub(:title, 'War and Peace') do
  assert_equal 'War and Peace', book.title
end