diff --git a/actionpack/test/controller/api/data_streaming_test.rb b/actionpack/test/controller/api/data_streaming_test.rb
index 6446ff9e40e774932b87c3e4cd6c421475c1f691..6081168e1c5c3a84b08b983fa86e12ef9ccea7b6 100644
--- a/actionpack/test/controller/api/data_streaming_test.rb
+++ b/actionpack/test/controller/api/data_streaming_test.rb
@@ -4,7 +4,7 @@
 
 module TestApiFileUtils
   def file_path() __FILE__ end
-  def file_data() @data ||= File.open(file_path, "rb") { |f| f.read } end
+  def file_data() @data ||= File.binread(file_path) end
 end
 
 class DataStreamingApiController < ActionController::API
diff --git a/actionpack/test/controller/send_file_test.rb b/actionpack/test/controller/send_file_test.rb
index c917cdf761202ee8740187faf73ab18da9ed939a..338405d5eeac87a4525c896cf269b49b7e0c5573 100644
--- a/actionpack/test/controller/send_file_test.rb
+++ b/actionpack/test/controller/send_file_test.rb
@@ -5,7 +5,7 @@
 module TestFileUtils
   def file_name() File.basename(__FILE__) end
   def file_path() __FILE__ end
-  def file_data() @data ||= File.open(file_path, "rb") { |f| f.read } end
+  def file_data() @data ||= File.binread(file_path) end
 end
 
 class SendFileController < ActionController::Base
diff --git a/activerecord/lib/active_record/fixture_set/render_context.rb b/activerecord/lib/active_record/fixture_set/render_context.rb
index 4f4f542fe7db8da6bfc9bafbfbbaf6c6e85a9aea..b6ca84192f3135d4e38871d60afd8a9f5a8bedfa 100644
--- a/activerecord/lib/active_record/fixture_set/render_context.rb
+++ b/activerecord/lib/active_record/fixture_set/render_context.rb
@@ -10,7 +10,7 @@ def get_binding
       end
 
       def binary(path)
-        %(!!binary "#{Base64.strict_encode64(File.read(path, mode: 'rb'))}")
+        %(!!binary "#{Base64.strict_encode64(File.binread(path))}")
       end
     end
   end
diff --git a/activerecord/test/cases/fixtures_test.rb b/activerecord/test/cases/fixtures_test.rb
index c5134b7775583c408dbf87c1b0ce7bab7fd09726..106389b1546478cd3d0c0f4e9e8465da335fe517 100644
--- a/activerecord/test/cases/fixtures_test.rb
+++ b/activerecord/test/cases/fixtures_test.rb
@@ -529,7 +529,7 @@ def test_subsubdir_file_with_arbitrary_name
   end
 
   def test_binary_in_fixtures
-    data = File.open(ASSETS_ROOT + "/flowers.jpg", "rb") { |f| f.read }
+    data = File.binread(ASSETS_ROOT + "/flowers.jpg")
     data.force_encoding("ASCII-8BIT")
     data.freeze
     assert_equal data, @flowers.data
diff --git a/railties/test/application/mailer_previews_test.rb b/railties/test/application/mailer_previews_test.rb
index c493add7ad1d2204a1f1b81e7f3b3ef975ff6e16..b948f32e566eb65f81f0b232f55e212b5dcc56db 100644
--- a/railties/test/application/mailer_previews_test.rb
+++ b/railties/test/application/mailer_previews_test.rb
@@ -611,7 +611,7 @@ class Notifier < ActionMailer::Base
           default from: "from@example.com"
 
           def foo
-            attachments['pixel.png'] = File.read("#{app_path}/public/images/pixel.png", mode: 'rb')
+            attachments['pixel.png'] = File.binread("#{app_path}/public/images/pixel.png")
             mail to: "to@example.org"
           end
         end
@@ -648,7 +648,7 @@ class Notifier < ActionMailer::Base
           default from: "from@example.com"
 
           def foo
-            attachments['pixel.png'] = File.read("#{app_path}/public/images/pixel.png", mode: 'rb')
+            attachments['pixel.png'] = File.binread("#{app_path}/public/images/pixel.png")
             mail to: "to@example.org"
           end
         end
@@ -693,7 +693,7 @@ class Notifier < ActionMailer::Base
           default from: "from@example.com"
 
           def foo
-            attachments['pixel.png'] = File.read("#{app_path}/public/images/pixel.png", mode: 'rb')
+            attachments['pixel.png'] = File.binread("#{app_path}/public/images/pixel.png")
             mail to: "to@example.org"
           end
         end