CFINSPEC-82: Add unit test and documentation for ppa resource

Signed-off-by: Sonu Saha <sonu.saha@progress.com>

docs-chef-io/content/inspec/resources/ppa.md

@@ -0,0 +1,66 @@
++++
+title = "ppa resource"
+draft = false
+gh_repo = "inspec"
+platform = "linux"
+
+[menu]
+  [menu.inspec]
+    title = "ppa"
+    identifier = "inspec/resources/os/ppa.md ppa resource"
+    parent = "inspec/resources/os"
++++
+
+Use the `ppa` Chef InSpec audit resource to verify PPA repositories on Debian-based linux distributions. Personal Package Archives (PPAs) are software repositories designed for Ubuntu users and are easier to install than other third-party repositories.
+
+The following ppa formats are supported:
+- `ubuntu-wine/ppa`
+- `ppa:ubuntu-wine/ppa`
+- `http://ppa.launchpad.net/juju/stable/ubuntu`
+
+## Availability
+
+### Installation
+
+This resource is distributed along with Chef InSpec itself. You can use it automatically.
+
+## Syntax
+
+A `ppa` Chef InSpec audit resource verifies PPA repositories on Debian-based linux distributions
+
+    describe ppa('path) do
+      it { should exist }
+      it { should be_enabled }
+    end
+where
+
+- `ppa('path')` must specify a PPA repository
+- `exist` and `be_enabled` are a valid matchers for this resource
+
+## Matchers
+
+For a full list of available matchers, please visit our [matchers page](https://docs.chef.io/inspec/matchers/).
+
+The specific matchers of this resource are: `exist` and `be_enabled`
+
+### exist
+
+The `exist` matcher tests if a repository exists on the system:
+
+    it { should exist }
+
+### be_enabled
+
+The `be_enabled` matcher tests if a repository is enabled on the system:
+
+    it { should be_enabled }
+## Examples
+The following example shows how to use this Chef InSpec audit resource.
+
+### Verify that a PPA repository exists and is enabled
+
+    describe ppa('ppa:nginx/stable') do
+      it { should exist }
+      it { should be_enabled }
+    end
+

test/unit/resources/ppa_test.rb

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+require "inspec/globals"
+require "#{Inspec.src_root}/test/helper"
+require_relative "../../../lib/inspec/resources/ppa"
+
+describe Inspec::Resources::PpaRepository do
+
+  it "checks on ubuntu as name/ppa" do
+    resource = MockLoader.new(:ubuntu).load_resource("ppa", "ubuntu-wine/ppa")
+    _(resource.exists?).must_equal true
+    _(resource.enabled?).must_equal true
+  end
+
+  it "checks on ubuntu as ppa:name/ppa" do
+    resource = MockLoader.new(:ubuntu).load_resource("ppa", "ppa:ubuntu-wine/ppa")
+    _(resource.exists?).must_equal true
+    _(resource.enabled?).must_equal true
+  end
+
+  it "checks on mint as name/ppa" do
+    resource = MockLoader.new(:mint18).load_resource("ppa", "ubuntu-wine/ppa")
+    _(resource.exists?).must_equal true
+    _(resource.enabled?).must_equal true
+  end
+
+  it "checks on mint as ppa:name/ppa" do
+    resource = MockLoader.new(:mint18).load_resource("ppa", "ppa:ubuntu-wine/ppa")
+    _(resource.exists?).must_equal true
+    _(resource.enabled?).must_equal true
+  end
+
+  it "checks on debian as http://name/" do
+    resource = MockLoader.new(:debian8).load_resource("ppa", "http://archive.ubuntu.com/ubuntu/")
+    _(resource.exists?).must_equal true
+    _(resource.enabled?).must_equal true
+  end
+
+  it "checks on unknown os" do
+    resource = MockLoader.new(:undefined).load_resource("ppa", "ubuntu-wine/ppa")
+    _(resource.exists?).must_equal false
+    _(resource.enabled?).must_equal false
+  end
+end