make example test wiki a git repo and test it

test/test_repo.rb

@@ -1,8 +1,15 @@
 require 'helper'
 
-class RepoTest < Test::Unit::TestCase
-  def test_repo_creation
-    repo = Gollum::Repo.new("examples/lotr")
-    assert_equal "examples/lotr", repo.path
+context "Repo" do
+  setup do
+    @repo = Gollum::Repo.new("examples/lotr.git")
+  end
+
+  test "repo path" do
+    assert_equal "examples/lotr.git", @repo.path
+  end
+
+  test "git repo" do
+    assert_equal Grit::Repo, @repo.repo.class
   end
 end