Convert tests to use plain rspec-puppet

Tests in the new style produces the following documentation output:

abs
  should not eq nil
  should run abs() and raise an Puppet::ParseError
  should run abs(-34) and return 34
  should run abs("-34") and return 34
  should run abs(34) and return 34
  should run abs("34") and return 34

1 files changed, 16 insertions, 16 deletions

diff --git a/spec/functions/sort_spec.rb b/spec/functions/sort_spec.rb
index 4c2a66c..9abd039 100755
--- a/spec/functions/sort_spec.rb
+++ b/spec/functions/sort_spec.rb
@@ -1,24 +1,24 @@
-#! /usr/bin/env ruby -S rspec
 require 'spec_helper'
 
-describe "the sort function" do
-  let(:scope) { PuppetlabsSpec::PuppetInternals.scope }
-
-  it "should exist" do
-    expect(Puppet::Parser::Functions.function("sort")).to eq("function_sort")
-  end
-
-  it "should raise a ParseError if there is not 1 arguments" do
-    expect { scope.function_sort(['','']) }.to( raise_error(Puppet::ParseError))
+describe 'sort' do
+  describe 'signature validation' do
+    it { is_expected.not_to eq(nil) }
+    it { is_expected.to run.with_params().and_raise_error(Puppet::ParseError, /wrong number of arguments/i) }
+    it { is_expected.to run.with_params([], 'extra').and_raise_error(Puppet::ParseError, /wrong number of arguments/i) }
+    it { pending('stricter input checking'); is_expected.to run.with_params({}).and_raise_error(Puppet::ParseError, /requires string or array/) }
+    it { pending('stricter input checking'); is_expected.to run.with_params(1).and_raise_error(Puppet::ParseError, /requires string or array/) }
+    it { pending('stricter input checking'); is_expected.to run.with_params(true).and_raise_error(Puppet::ParseError, /requires string or array/) }
   end
 
-  it "should sort an array" do
-    result = scope.function_sort([["a","c","b"]])
-    expect(result).to(eq(['a','b','c']))
+  context 'when called with an array' do
+    it { is_expected.to run.with_params([]).and_return([]) }
+    it { is_expected.to run.with_params(['a']).and_return(['a']) }
+    it { is_expected.to run.with_params(['c', 'b', 'a']).and_return(['a', 'b', 'c']) }
   end
 
-  it "should sort a string" do
-    result = scope.function_sort(["acb"])
-    expect(result).to(eq('abc'))
+  context 'when called with a string' do
+    it { is_expected.to run.with_params('').and_return('') }
+    it { is_expected.to run.with_params('a').and_return('a') }
+    it { is_expected.to run.with_params('cbda').and_return('abcd') }
   end
 end