diff --git a/Rakefile b/Rakefile
index fb960e0..6971711 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,4 +1,5 @@
 require "bundler/gem_tasks"
+require 'rake/testtask'
 
 task :examples do
   $LOAD_PATH.unshift File.expand_path('../examples', __FILE__)
@@ -7,3 +8,7 @@ task :examples do
   require 'recursive'
 end
 
+Rake::TestTask.new do |t|
+  t.libs << "test"
+  t.test_files = FileList['test/*_test.rb']
+end
diff --git a/lib/parser_combinator.rb b/lib/parser_combinator.rb
index d208862..18fb233 100644
--- a/lib/parser_combinator.rb
+++ b/lib/parser_combinator.rb
@@ -210,7 +210,7 @@ def self.ok(object)
   end
 
   def self.fail(status=nil)
-    new{|i| Fail.new(status)}
+    new{Fail.new(status)}
   end
 
   def self.so_then(parser, &continuation_proc)
diff --git a/test/parser_combinator_test.rb b/test/parser_combinator_test.rb
new file mode 100644
index 0000000..85edda2
--- /dev/null
+++ b/test/parser_combinator_test.rb
@@ -0,0 +1,7 @@
+require 'test_helper'
+
+class ParserCombinatorTest < Test::Unit::TestCase
+  def test_fail
+    assert_instance_of ParserCombinator, ParserCombinator.fail
+  end
+end
diff --git a/test/test_helper.rb b/test/test_helper.rb
new file mode 100644
index 0000000..b4cc915
--- /dev/null
+++ b/test/test_helper.rb
@@ -0,0 +1,4 @@
+require "test-unit"
+
+$LOAD_PATH << File.join(__dir__, "../lib")
+require "parser_combinator"