Allow for stepdown of minor versions

README.md

@@ -219,7 +219,7 @@ end
 
 ### Testing a function
 
-As with testing manifests, types, or providers, `on_supported_os` iteration simplifies your function unit tests. 
+As with testing manifests, types, or providers, `on_supported_os` iteration simplifies your function unit tests.
 
 **Specifying each operating system**:
 
@@ -275,7 +275,7 @@ describe 'myfunction' do
 end
 ```
 
-### Adding custom fact values 
+### Adding custom fact values
 
 By adding custom fact values, you can:
 
@@ -352,11 +352,10 @@ In addition to the static fact values shown in the previous examples, you can cr
 To do this, pass a lambda as the value for the custom fact. The lambda is passed the same values for operating system name and fact values that your tests are provided by `on_supported_os`.
 
 ```ruby
-add_custom_fact :root_home, lambda { |os,facts| "/tmp/#{facts['hostname']" }
+add_custom_fact :root_home, lambda { |os,facts| "/tmp/#{facts['hostname']}" }
 ```
 
-Running your tests
-------------------
+## Running your tests
 
 For most cases, there is no change to how you run your tests. Running `rake spec` will run all the tests against the facts for all the supported operating systems.
 
@@ -365,3 +364,5 @@ If you want to run the tests against the facts for specific operating systems, y
 ```bash
 SPEC_FACTS_OS='ubuntu-14' rake spec
 ```
+
+When no facts are available for the specific facter/operating system combination, the library will fall back to facts from earlier versions of the requested operating system, to allow testing to continue when new versions of facter are released. Set `SPEC_FACTS_STRICT=yes` to instead trigger a failure.

lib/rspec-puppet-facts.rb

@@ -39,6 +39,15 @@ def on_supported_os(opts = {})
     end
 
     facter_version_filter = RspecPuppetFacts.facter_version_to_filter(facterversion)
+    db = FacterDB.get_facts({ :facterversion =>  facter_version_filter })
+
+    version = facterversion
+    while db.empty? && version !~ /\d+\.0\.\d+/
+      version = RspecPuppetFacts.down_facter_version(version)
+      facter_version_filter = RspecPuppetFacts.facter_version_to_filter(version)
+      db = FacterDB.get_facts({ :facterversion =>  facter_version_filter})
+    end
+
 
     filter = []
     opts[:supported_os].map do |os_sup|
@@ -79,6 +88,14 @@ def on_supported_os(opts = {})
       return {}
     end
 
+    unless version == facterversion
+      if RspecPuppetFacts.spec_facts_strict?
+        raise ArgumentError, "No facts were found in the FacterDB for Facter v#{facterversion}, aborting"
+      else
+        RspecPuppetFacts.warning "No facts were found in the FacterDB for Facter v#{facterversion}, using v#{version} instead"
+      end
+    end
+
     os_facts_hash = {}
     received_facts.map do |facts|
       # Fix facter bug
@@ -161,6 +178,13 @@ def self.spec_facts_os_filter
     ENV['SPEC_FACTS_OS']
   end
 
+  # If SPEC_FACTS_STRICT is set to `yes`, RspecPuppetFacts will error on missing FacterDB entries, instead of warning & skipping the tests, or using an older facter version.
+  # @return [Boolean]
+  # @api private
+  def self.spec_facts_strict?
+    ENV['SPEC_FACTS_STRICT'] == 'yes'
+  end
+
   # These facts are common for all OS'es and will be
   # added to the facts retrieved from the FacterDB
   # @api private
@@ -238,4 +262,15 @@ def self.facter_version_to_filter(version)
     major, minor = version.split('.')
     "/\\A#{major}\\.#{minor}\\./"
   end
+  # Subtracts from the minor version passed and returns a string representing
+  # the next minor version down
+  # @return [String] next version below
+  # @param version [String] the Facter version
+  # @param minor_subtractor [int] the value which to subtract by
+  # @api private
+  def self.down_facter_version(version, minor_subtractor = 1)
+      major, minor, z = version.split('.')
+      minor = (minor.to_i - minor_subtractor).to_s
+      "#{major}.#{minor}.#{z}"
+  end
 end

spec/rspec_puppet_facts_spec.rb

@@ -372,6 +372,9 @@
     end
 
     context 'Without a custom facterversion in the options hash' do
+      before(:each) do
+        allow(Facter).to receive(:version).and_return('2.4.5')
+      end
       subject do
         on_supported_os(
           supported_os: [
@@ -381,13 +384,45 @@
       end
 
       it 'returns facts from the loaded facter version' do
+        is_expected.to match(
+          'centos-7-x86_64' => include(
+            facterversion: /\A2\.4\./
+          )
+        )
+      end
+    end
+
+    context 'With a version that is above the current gem' do
+      before(:each) do
+        allow(Facter).to receive(:version).and_return('2.4.5')
+      end
+
+      subject do
+        on_supported_os(
+          supported_os: [
+            { 'operatingsystem' => 'CentOS', 'operatingsystemrelease' => %w[7] }
+          ],
+          facterversion: "2.5"
+        )
+      end
+
+      it 'returns facts from a facter version matching future and below' do
         major, minor = Facter.version.split('.')
         is_expected.to match(
           'centos-7-x86_64' => include(
-            facterversion: /\A#{major}\.#{minor}\./
+            facterversion: /\A2\.4\./
           )
         )
       end
+
+      context 'With SPEC_FACTS_STRICT set to `yes`' do
+        before(:each) do
+          allow(RspecPuppetFacts).to receive(:spec_facts_strict?).and_return(true)
+        end
+        it 'errors' do
+          expect { subject }.to raise_error ArgumentError, /No facts were found in the FacterDB.*aborting/
+        end
+      end
     end
 
     context 'With a custom facterversion (3.1) in the options hash' do