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, 12 insertions, 30 deletions

diff --git a/spec/functions/downcase_spec.rb b/spec/functions/downcase_spec.rb
index edebc44..c594560 100755
--- a/spec/functions/downcase_spec.rb
+++ b/spec/functions/downcase_spec.rb
@@ -1,33 +1,15 @@
-#! /usr/bin/env ruby -S rspec
 require 'spec_helper'
 
-describe "the downcase function" do
-  let(:scope) { PuppetlabsSpec::PuppetInternals.scope }
-
-  it "should exist" do
-    expect(Puppet::Parser::Functions.function("downcase")).to eq("function_downcase")
-  end
-
-  it "should raise a ParseError if there is less than 1 arguments" do
-    expect { scope.function_downcase([]) }.to( raise_error(Puppet::ParseError))
-  end
-
-  it "should downcase a string" do
-    result = scope.function_downcase(["ASFD"])
-    expect(result).to(eq("asfd"))
-  end
-
-  it "should do nothing to a string that is already downcase" do
-    result = scope.function_downcase(["asdf asdf"])
-    expect(result).to(eq("asdf asdf"))
-  end
-
-  it "should accept objects which extend String" do
-    class AlsoString < String
-    end
-
-    value = AlsoString.new("ASFD")
-    result = scope.function_downcase([value])
-    result.should(eq('asfd'))
-  end
+describe 'downcase' do
+  it { is_expected.not_to eq(nil) }
+  it { is_expected.to run.with_params().and_raise_error(Puppet::ParseError) }
+  it { is_expected.to run.with_params(100).and_raise_error(Puppet::ParseError) }
+  it { is_expected.to run.with_params("abc").and_return("abc") }
+  it { is_expected.to run.with_params("Abc").and_return("abc") }
+  it { is_expected.to run.with_params("ABC").and_return("abc") }
+
+  it { is_expected.to run.with_params(AlsoString.new("ABC")).and_return("abc") }
+  it { is_expected.to run.with_params([]).and_return([]) }
+  it { is_expected.to run.with_params(["ONE", "TWO"]).and_return(["one", "two"]) }
+  it { is_expected.to run.with_params(["One", 1, "Two"]).and_return(["one", 1, "two"]) }
 end