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/grep_spec.rb b/spec/functions/grep_spec.rb
index 9c671dd..6e0bd6e 100755
--- a/spec/functions/grep_spec.rb
+++ b/spec/functions/grep_spec.rb
@@ -1,19 +1,19 @@
-#! /usr/bin/env ruby -S rspec
 require 'spec_helper'
 
-describe "the grep function" do
-  let(:scope) { PuppetlabsSpec::PuppetInternals.scope }
-
-  it "should exist" do
-    expect(Puppet::Parser::Functions.function("grep")).to eq("function_grep")
-  end
-
-  it "should raise a ParseError if there is less than 1 arguments" do
-    expect { scope.function_grep([]) }.to( raise_error(Puppet::ParseError))
-  end
-
-  it "should grep contents from an array" do
-    result = scope.function_grep([["aaabbb","bbbccc","dddeee"], "bbb"])
-    expect(result).to(eq(["aaabbb","bbbccc"]))
-  end
+describe 'grep' 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('one').and_raise_error(Puppet::ParseError, /wrong number of arguments/i) }
+  it {
+    pending("grep does not actually check this, and raises NoMethodError instead")
+    is_expected.to run.with_params('one', 'two').and_raise_error(Puppet::ParseError, /first argument not an array/)
+  }
+  it {
+    pending("grep does not actually check this, and raises NoMethodError instead")
+    is_expected.to run.with_params(1, 'two').and_raise_error(Puppet::ParseError, /first argument not an array/)
+  }
+  it { is_expected.to run.with_params('one', 'two', 'three').and_raise_error(Puppet::ParseError, /wrong number of arguments/i) }
+  it { is_expected.to run.with_params([], 'two').and_return([]) }
+  it { is_expected.to run.with_params(['one', 'two', 'three'], 'two').and_return(['two']) }
+  it { is_expected.to run.with_params(['one', 'two', 'three'], 't(wo|hree)').and_return(['two', 'three']) }
 end