Add tests for valid/invalid resource names

Prior to this commit, ppa_spec.rb did not test the recently implemented
validation for resource names.

This commit aims to implement some test cases to make sure that valid
resource names are allowed while invalid or malicious resource names do
not work.

spec/defines/ppa_spec.rb

@@ -43,6 +43,69 @@ def ppa_exec_params(user, repo, distro = 'trusty', environment = [])
     }
   end
 
+  [
+    'ppa:foo/bar',
+    'ppa:foo/bar1.0',
+    'ppa:foo10/bar10',
+    'ppa:foo-/bar_',
+  ].each do |value|
+    describe 'valid resource names' do
+      let :facts do
+        {
+          os: {
+            family: 'Debian',
+            name: 'Ubuntu',
+            release: {
+              major: '18',
+              full: '18.04',
+            },
+            distro: {
+              codename: 'trusty',
+              id: 'Ubuntu',
+            },
+          },
+        }
+      end
+
+      let(:title) { value }
+
+      it { is_expected.not_to raise_error }
+      it { is_expected.to contain_exec("add-apt-repository-#{value}") }
+    end
+  end
+
+  [
+    'ppa:foo!/bar',
+    'ppa:foo/bar!',
+    'ppa:foo1.0/bar',
+    'ppa:foo/bar/foobar',
+    '|| ls -la ||',
+    '|| touch /tmp/foo.txt ||',
+  ].each do |value|
+    describe 'invalid resource names' do
+      let :facts do
+        {
+          os: {
+            family: 'Debian',
+            name: 'Ubuntu',
+            release: {
+              major: '18',
+              full: '18.04',
+            },
+            distro: {
+              codename: 'trusty',
+              id: 'Ubuntu',
+            },
+          },
+        }
+      end
+
+      let(:title) { value }
+
+      it { is_expected.to raise_error(Puppet::PreformattedError, %r{Invalid PPA name: #{value}}) }
+    end
+  end
+
   describe 'Ubuntu 15.10 sources.list filename' do
     let :facts do
       {