diff --git a/.rubocop.yml b/.rubocop.yml
index 9db88cbbdf..e93e7ff82f 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -9,6 +9,10 @@ AllCops:
     - 'actionpack/lib/action_dispatch/journey/parser.rb'
     - 'railties/test/fixtures/tmp/**/*'
 
+Performance:
+  Exclude:
+    - '**/test/**/*'
+
 Rails:
   Enabled: true
 
diff --git a/actionpack/test/dispatch/header_test.rb b/actionpack/test/dispatch/header_test.rb
index 43e63eb996..bd2a5b35fb 100644
--- a/actionpack/test/dispatch/header_test.rb
+++ b/actionpack/test/dispatch/header_test.rb
@@ -105,20 +105,16 @@ def make_headers(hash)
   end
 
   test "#merge! headers with mutation" do
-    # rubocop:disable Performance/RedundantMerge
     @headers.merge!("Host" => "http://example.test",
                     "Content-Type" => "text/html")
-    # rubocop:enable Performance/RedundantMerge
     assert_equal({ "HTTP_HOST" => "http://example.test",
                   "CONTENT_TYPE" => "text/html",
                   "HTTP_REFERER" => "/some/page" }, @headers.env)
   end
 
   test "#merge! env with mutation" do
-    # rubocop:disable Performance/RedundantMerge
     @headers.merge!("HTTP_HOST" => "http://first.com",
                     "CONTENT_TYPE" => "text/html")
-    # rubocop:enable Performance/RedundantMerge
     assert_equal({ "HTTP_HOST" => "http://first.com",
                   "CONTENT_TYPE" => "text/html",
                   "HTTP_REFERER" => "/some/page" }, @headers.env)
diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index 3ca15640fd..fbeb617b29 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -187,7 +187,7 @@ def self.sanitize_sql(args)
       end
 
       relation = Relation.new(klass)
-      relation.merge!(where: ["foo = ?", "bar"]) # rubocop:disable Performance/RedundantMerge
+      relation.merge!(where: ["foo = ?", "bar"])
       assert_equal Relation::WhereClause.new(["foo = bar"]), relation.where_clause
     end