diff --git a/.rspec b/.rspec
new file mode 100644
index 00000000..608d28f4
--- /dev/null
+++ b/.rspec
@@ -0,0 +1,4 @@
+--color
+--order rand
+--require spec_helper
+--warning
diff --git a/Rakefile b/Rakefile
index c8f346b8..ab29abd3 100644
--- a/Rakefile
+++ b/Rakefile
@@ -14,10 +14,7 @@ RuboCop::RakeTask.new(:rubocop) do |task|
   task.options += ['--force-exclusion', 'lib/one_gadget/builds/*.rb']
 end
 
-RSpec::Core::RakeTask.new(:spec) do |task|
-  task.pattern = './spec/**/*_spec.rb'
-  task.rspec_opts = ['--color', '--require spec_helper', '--order rand', '--warning']
-end
+RSpec::Core::RakeTask.new(:spec)
 
 YARD::Rake::YardocTask.new(:doc) do |t|
   t.files = Dir['lib/**/*.rb'] - Dir['lib/one_gadget/builds/*.rb']
diff --git a/lib/one_gadget/gadget.rb b/lib/one_gadget/gadget.rb
index 8fcb4b5e..264861c7 100644
--- a/lib/one_gadget/gadget.rb
+++ b/lib/one_gadget/gadget.rb
@@ -81,7 +81,7 @@ def calculate_score(cons)
     module ClassMethods
       # Path to the pre-build files.
       BUILDS_PATH = File.join(__dir__, 'builds').freeze
-      # Cache.
+      # Record.
       BUILDS = Hash.new { |h, k| h[k] = [] }
       # Get gadgets from pre-defined corpus.
       # @param [String] build_id Desired build id.
@@ -89,8 +89,8 @@ module ClassMethods
       #   When local not found, try search in latest version?
       # @return [Array<Gadget::Gadget>?] Gadgets.
       def builds(build_id, remote: true)
-        require_all if BUILDS.empty?
-        return BUILDS[build_id] if BUILDS.key?(build_id)
+        ret = find_build(build_id)
+        return ret unless ret.nil?
         return build_not_found unless remote
 
         # fetch remote builds
@@ -145,10 +145,11 @@ def add(build_id, offset, **options)
 
       private
 
-      def require_all
-        Dir.glob(File.join(BUILDS_PATH, '**', '*.rb')).each do |dic|
+      def find_build(id)
+        Dir.glob(File.join(BUILDS_PATH, "*-#{id}.rb")).each do |dic|
           require dic
         end
+        BUILDS[id] if BUILDS.key?(id)
       end
 
       def build_not_found