diff --git a/Gemfile b/Gemfile
index 033d8206..6257b7fc 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,3 +2,10 @@ source 'https://rubygems.org'
 
 # Specify your gem's dependencies in narray-devel.gemspec
 gemspec
+
+group :development do
+  gem 'rake', '>= 12.3.3'
+  gem 'rake-compiler', '~> 1.1'
+  gem 'test-unit'
+  gem 'yard'
+end
diff --git a/doc/note.md b/doc/note.md
index 5a569b0e..92026e85 100644
--- a/doc/note.md
+++ b/doc/note.md
@@ -1,21 +1,18 @@
 # Miscellaneous notes for Numo::NArray
 
-## Running RSpec
+## Running Tests
 
-(in advance, install gem with --development option)
+```shell
+# All tests
+bundle exec rake test
 
-  ```shell
-$ "${HOME}/.gem/ruby/2.?/bin/rspec" "${HOME}/.gem/ruby/2.?/gems/numo-narray-0.9.?.?/spec/bit_spec.rb"
-$ "${HOME}/.gem/ruby/2.?/bin/rspec" "${HOME}/.gem/ruby/2.?/gems/numo-narray-0.9.?.?/spec/narray_spec.rb"
+# Specific test
+bundle exec ruby test/narray_test.rb
+bundle exec ruby test/bit_test.rb
 ```
 
 ## YARD documents generation
 
-(in advance, install yard gem)
-
-  ```shell
-$ cd "${HOME}/.gem/ruby/2.?/gems/numo-narray-0.9.?.?/ext/numo/narray"
-$ make doc
-yard doc *.c types/*.c
-...
+```shell
+bundle exec rake doc
 ```
diff --git a/numo-narray.gemspec b/numo-narray.gemspec
index 48d1ba1f..511f50d3 100644
--- a/numo-narray.gemspec
+++ b/numo-narray.gemspec
@@ -27,8 +27,4 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
   spec.extensions    = ["ext/numo/narray/extconf.rb"]
-
-  spec.add_development_dependency "rake", ">= 12.3.3"
-  spec.add_development_dependency "rake-compiler", "~> 1.1"
-  spec.add_development_dependency "test-unit"
 end