How do you test code that forks using rspec

I have the following开发者_Python百科 code

  def start_sunspot_server
    unless @server
      pid = fork do
        STDERR.reopen("/dev/null")
        STDOUT.reopen("/dev/null")
        server.run
      end

      at_exit { Process.kill("TERM", pid) }

      wait_until_solr_starts
    end
  end

How would I effectively go about testing it using rspec?

I thought something along

Kernel.should_receive(:fork)
STDERR.should_receive(:reopen).with("/dev/null")
STDOUT.should_receive(:reopen).with("/dev/null")
server.should_receive(:run)

etc

---

I'm confused by the @server instance variable and server method in your example, but here is an example that should help you get where you're trying to go:

class Runner
  def run
    fork do
      STDERR.reopen("/dev/null")
    end
  end
end

describe "runner" do
  it "#run reopens STDERR at /dev/null" do
    runner = Runner.new

    runner.should_receive(:fork) do |&block|
      STDERR.should_receive(:reopen).with("/dev/null")
      block.call
    end

    runner.run
  end
end

The key is that the fork message is sent to the Runner object itself, even though its implementation is in the Kernel module.

HTH, David

---

David's solution didn't work for us. Maybe it's because we're not using RSpec 2?

Here's what did work.

def run
  fork do
    blah
  end
end

describe '#run' do
  it 'should create a fork which calls #blah' do
    subject.should_receive(:fork).and_yield do |block_context|
      block_context.should_receive(:blah)
    end

    subject.run_job
  end
end

I'm not sure how this would apply when calling a constant, such as STDERR, but this was the only way we were able to accomplish fork testing.