How can I stub find_each for rspec testing in rails 3

Question

I was wondering how to test a find_each call in rspec. I'm used to simply stubbing what I want my models to return so I don't rely on test data in the db like this:

MyClass.stub(:find).and_return(my_mock)

However, in another class I'm doing this:

MyClass.find_each do |instance_of_my_class|
  do_stuff_here_on(instance_of_my_class)
end

I find that if I do this:

MyClass.stub(:find_each).and_return([one_mock, two_mock])

in the spec test, the "do stuff here" part is not being executed. Does anyone know how to stub a find_each for rspec testing?

Answer 1

You can use and_yield to make rspec call the block passed to the mock:

MyClass.stub(:find_each).and_yield(one_mock).and_yield(two_mock)

Answer 2

The whole point of stubbing a method is so that the method returns an expected value and not execute its contents. If you have a bunch of logic within the find_each method, I would recommend moving it to a separate method and testing that logic separately. You can then test that your method is called during execution.

Here's a pretty high level example:

class Example1
  def my_method
    # some logic
  end
end

class Example2
  def my_other_method
    Example1.find_each(&:my_method)
  end
end

Rspec:

describe Example1 do
  it "should return something" do
    example = Example1.new
    example.my_method.should == something
  end
end

describe Example2 do
  it "should call my_method on Example1" do
    example1 = mock(:example1, :my_method => true)
    example2 = Example2.new

    example1.should_receive(:my_method)
    example2.my_other_method
  end
end

Answer 3

If you need to stub find_each on a verified double and have it loop through a specific array of values, you can do this:

let(:my_relation_with_mocked_find_each) do
  relation = instance_double('YourModel::ActiveRecord_Relation')

  receive_yield = receive(:find_each)

  fake_objs.each do |obj|
    receive_yield = receive_yield.and_yield(obj)
  end

  allow(relation).to receive_yield
  relation
end

Answer 4

This should do it:

MyClass.stub(:find_each) {|block|
  block.call
  [one_mock, two_mock]
}

If do_stuff_here_on isn't globally reachable, e.g. an instance method on some_object, you'll need some instance_eval to get the right scope for the block:

MyClass.stub(:find_each) {|block|
  some_object.instance_eval(&block)
  [one_mock, two_mock]
}