unbound_version: add spec tests to the unbound_version fact

lib/facter/unbound_version.rb

@@ -7,9 +7,13 @@
                 '/usr/sbin/unbound'
               end
 if File.exist? unbound_bin
-  unbound_version = Facter::Util::Resolution.exec(
-    "#{unbound_bin} -V 2>&1"
-  ).match(%r{Version\s+(\d+(?:\.\d+)*)})[1]
+  begin
+    unbound_version = Facter::Util::Resolution.exec(
+      "#{unbound_bin} -V 2>&1"
+    ).match(%r{Version\s+(\d+(?:\.\d+){2})\s+})[1]
+  rescue
+    unbound_version = 'UNKNOWN'
+  end
   Facter.add(:unbound_version) do
     setcode do
       unbound_version

spec/unit/unbound/facter/unbound_version_spec.rb

@@ -0,0 +1,43 @@
+require 'spec_helper'
+
+version_string = <<-VERSION
+unbound: invalid option -- 'V'
+usage:  unbound [options]
+        start unbound daemon DNS resolver.
+-h      this help
+-c file config file to read instead of /etc/unbound/unbound.conf
+        file format is described in unbound.conf(5).
+-d      do not fork into the background.
+-v      verbose (more times to increase verbosity)
+Version %s
+linked libs: libevent 2.0.21-stable (it uses epoll), OpenSSL 1.1.0l  10 Sep 2019
+linked modules: dns64 python validator iterator
+BSD licensed, see LICENSE in source package for details.
+Report bugs to unbound-bugs@nlnetlabs.nl
+VERSION
+
+tests = {
+  'valid' => ['1.1.1', '1.90.24', '1.0.404', '2.5.6'],
+  'invalid' => ['1', '1.1', '1.1.1.1', '1,1,1', '2:5.1', 'foobar']
+}
+describe Facter::Util::Fact.to_s do
+  before { Facter.clear }
+  tests.each_pair do |test, versions|
+    describe "test #{test} versions" do
+      versions.each do |version|
+        context "test version #{version}" do
+          before do
+            Facter::Util::Resolution.stubs(:exec).with('/usr/sbin/unbound -V 2>&1').returns(
+              version_string % version
+            )
+          end
+          if test == 'valid'
+            it { expect(Facter.fact(:unbound_version).value).to eq(version) }
+          else
+            it { expect(Facter.fact(:unbound_version).value).to eq('UNKNOWN') }
+          end
+        end
+      end
+    end
+  end
+end