Facter stubbing examples

fact_spec.rb

require 'rspec'
require 'facter'

describe 'facter_value' do
  context 'when stubbing Facter::Util::Collection#fact' do
    before(:each) do
      stub_fact = instance_double(Facter::Util::Fact, :value => 'foo')
      allow(Facter.collection).to receive(:fact).with(:test_fact).and_return(stub_fact)
    end

    it 'can be accessed via Facter.value' do
      expect(Facter.value(:test_fact)).to eq('foo')
    end

    it 'can be accessed via Facter::Util::Fact#value' do
      expect(Facter.fact(:test_fact).value).to eq('foo')
    end

    it 'is present in the fact collection' do
      expect(Facter.collection.fact(:test_fact)).not_to be_nil
    end
  end

  context 'when stubbing Facter::Util::Fact#value' do
    before(:each) do
      allow(Facter.fact(:test_fact)).to receive(:value).and_return('foo')
    end

    it 'can be accessed via Facter::Util::Fact#value' do
      expect(Facter.fact(:test_fact).value).to eq('foo')
    end

    it 'can not be accessed via Facter.value' do
      expect(Facter.value(:test_fact)).to be_nil
    end

    it 'is not actually present in the fact collection' do
      expect(Facter.collection.fact(:test_fact)).to be_nil
    end
  end
end

host_type.rb

Facter.add('host_type') do
  setcode do
    type = 'unknown'
    if Facter.value(:ec2_metadata)
      type = 'aws'
    end
    if Facter.value(:cloud)
      if Facter.value(:cloud)['provider'] == 'azure'
        type = 'azure'
      end
      if Facter.value(:cloud)['provider'] == 'google'
        type = 'gcp'
      end
    end
    type
  end
end

host_type_spec.rb

require 'spec_helper'

describe 'custom fact host_type', type: :fact do
  context 'supported operating systems' do
    on_supported_os(requested_facterversion).each do |os, _facts|
      context "on #{os}" do
        before(:each) do
          Facter.flush
          allow(Facter.collection).to receive(:fact).with(anything).and_call_original
        end

        describe 'amazon' do
          before(:each) do
            stub_fact = instance_double(Facter::Util::Fact, value: {})
            allow(Facter.collection).to receive(:fact).with(:ec2_metadata).and_return(stub_fact)
          end
          it do
            expect(Facter.fact(:host_type).value).to eq('aws')
          end
        end
        describe 'azure' do
          let(:cloud) { { 'provider' => 'azure', 'metadata' => {} } }

          before(:each) do
            stub_fact = instance_double(Facter::Util::Fact, value: cloud)
            allow(Facter.collection).to receive(:fact).with(:cloud).and_return(stub_fact)
          end
          it do
            expect(Facter.fact(:host_type).value).to eq('azure')
          end
        end
        describe 'google' do
          let(:cloud) { { 'provider' => 'google', 'metadata' => {} } }

          before(:each) do
            stub_fact = instance_double(Facter::Util::Fact, value: cloud)
            allow(Facter.collection).to receive(:fact).with(:cloud).and_return(stub_fact)
          end
          it do
            expect(Facter.fact(:host_type).value).to eq('gcp')
          end
        end
        describe 'unknown host_type' do
          before(:each) do
            allow(Facter.collection).to receive(:fact).with(:ec2_metadata).and_return(nil)
          end
          it do
            expect(Facter.fact(:host_type).value).to eq('unknown')
          end
        end
      end
    end
  end
end

output.txt

puppet/profile_base - [dev●] » be rspec spec/unit/facter/host_type_spec.rb

custom fact host_type
  supported operating systems
    on ubuntu-14.04-x86_64
      amazon
        should eq "aws"
      azure
        should eq "azure"
      google
        should eq "gcp"
      unknown host_type
        should eq "unknown"
    on ubuntu-16.04-x86_64
      amazon
        should eq "aws"
      azure
        should eq "azure"
      google
        should eq "gcp"
      unknown host_type
        should eq "unknown"
    on windows-2012 R2-x86_64
      amazon
        should eq "aws"
      azure
        should eq "azure"
      google
        should eq "gcp"
      unknown host_type
        should eq "unknown"
    on centos-7-x86_64
      amazon
        should eq "aws"
      azure
        should eq "azure"
      google
        should eq "gcp"
      unknown host_type
        should eq "unknown"
    on centos-6-x86_64
      amazon
        should eq "aws"
      azure
        should eq "azure"
      google
        should eq "gcp"
      unknown host_type
        should eq "unknown"