diff --git a/Gemfile b/Gemfile
index ecba232..734dd77 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,3 +8,5 @@ gemspec
 gem "minitest"
 gem "rake"
 gem "rubocop"
+
+gem "minitest-mock" if Gem::Version.create(RUBY_VERSION) >= Gem::Version.create("3.1")
diff --git a/test/test_helper.rb b/test/test_helper.rb
index a3a6e16..cac50ab 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -3,6 +3,7 @@
 $LOAD_PATH.unshift File.expand_path("../lib", __dir__)
 require "omniauth/twitter2"
 
+require "minitest/mock"
 require "minitest/autorun"
 
 def mock_auth_sample # rubocop:disable Metrics/MethodLength