Add minitest as a dependency and upgrade tests

Author: tiennou

docurium.gemspec

@@ -22,6 +22,7 @@ Gem::Specification.new do |s|
   s.add_dependency "ffi-clang", "~> 0.5"
   s.add_development_dependency "bundler",   "~>1.0"
   s.add_development_dependency "rake", "~> 12"
+  s.add_development_dependency "minitest", "~> 5.11"
 
   s.files         = `git ls-files`.split("\n")
   s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")

test/repo_test.rb renamed to test/docurium_test.rb

@@ -2,7 +2,7 @@
 require 'docurium'
 require 'rugged'
 
-class DocuriumTest < MiniTest::Unit::TestCase
+class DocuriumTest < Minitest::Test
 
   def setup
     @dir = Dir.mktmpdir()

test/gen_test.rb

@@ -3,7 +3,7 @@
 require 'docurium/cli'
 require 'tempfile'
 
-class GenTest < MiniTest::Unit::TestCase
+class GenTest < Minitest::Test
 
   # make sure we can read what we give the user
   def test_read_generated_file

test/parser_test.rb

@@ -2,7 +2,7 @@
 require 'docurium'
 require 'pp'
 
-class TestParser < Minitest::Unit::TestCase
+class ParserTest < Minitest::Test
 
   def setup
     @parser = Docurium::DocParser.new