Mocking Files during a ChefSpec run

Question

I created a Chef resource which 'extends' the deploy resource of chef. The basic idea is to check for the existence of a file deploy/crontab similar to mechanisms deploy/after_restart.rb in the source to be deployed, and create cronjobs out of it.

While this mechanism works as it should be (see https://github.com/fh/easybib-cookbooks/blob/t/cron-tests/easybib/providers/deploy.rb#L11-L14), I am struggling with a ChefSpec based test for it. I am currently trying to create mocks using FakeFS - but when I mock the Filesystem before the Chef run, the run fails because no cookbooks are found, since they do not exist in the mocked filesystem. If I dont, the mocked file deploy/crontab is obviously not found, so the provider doesnt do anything. My current approach is to trigger FakeFS.activate! directly before runner.converge(described_recipe) in the chef_run.

I would love to hear some recommendations how to do a proper test here: Is there maybe some possiblity to enable the FakeFS only directly before the deploy-resource-run, or to mock the Filesystem only partially?

Answer 1

I had a similar problem stubbing the File system classes. The way that I have been solving this problem is as follows.

::File.stub(:exists?).with(anything).and_call_original
::File.stub(:exists?).with('/tmp/deploy/crontab').and_return true

open_file = double('file')
allow(open_file).to receive(:each_line).and_yield('line1').and_yield('line2')

::File.stub(:open).and_call_original
::File.stub(:open).with('/tmp/deploy/crontab').and_return open_file

Answer 2

Since punkle's solutions is syntactically deprecated and there are some parts missing, I'll try to give a new solution:

require 'spec_helper'

describe 'cookbook::recipe' do

  let(:chef_run) { ChefSpec::SoloRunner.converge(described_recipe) }


  file_content = <<-EOF
...here goes your
multiline
file content
EOF

  describe 'describe what your recipe should do' do

    before(:each) do
      allow(File).to receive(:exists?).with(anything).and_call_original
      allow(File).to receive(:exists?).with('/path/to/file/that/should/exist').and_return true
      allow(File).to receive(:read).with(anything).and_call_original
      allow(File).to receive(:read).with('/path/to/file/that/should/exist').and_return file_content
    end

    it 'describe what should happen with the file...' do
      expect(chef_run).to #...
    end
  end

end