1 files changed, 37 insertions, 6 deletions
diff --git a/railties/test/application/middleware_test.rb b/railties/test/application/middleware_test.rb
index 9baf7360a5..0a6e5b52e9 100644
--- a/railties/test/application/middleware_test.rb
+++ b/railties/test/application/middleware_test.rb
@@ -30,10 +30,10 @@ module ApplicationTests
         "Rack::Runtime",
         "Rack::MethodOverride",
         "ActionDispatch::RequestId",
-        "Rails::Rack::Logger", # must come after Rack::MethodOverride to properly log overridden methods
+        "ActionDispatch::RemoteIp",
+        "Rails::Rack::Logger",
         "ActionDispatch::ShowExceptions",
         "ActionDispatch::DebugExceptions",
-        "ActionDispatch::RemoteIp",
         "ActionDispatch::Reloader",
         "ActionDispatch::Callbacks",
         "ActiveRecord::Migration::CheckPending",
@@ -58,10 +58,10 @@ module ApplicationTests
         "ActiveSupport::Cache::Strategy::LocalCache",
         "Rack::Runtime",
         "ActionDispatch::RequestId",
-        "Rails::Rack::Logger", # must come after Rack::MethodOverride to properly log overridden methods
+        "ActionDispatch::RemoteIp",
+        "Rails::Rack::Logger",
         "ActionDispatch::ShowExceptions",
         "ActionDispatch::DebugExceptions",
-        "ActionDispatch::RemoteIp",
         "ActionDispatch::Reloader",
         "ActionDispatch::Callbacks",
         "Rack::Head",
@@ -70,6 +70,37 @@ module ApplicationTests
       ], middleware
     end
 
+    test "middleware dependencies" do
+      boot!
+
+      # The following array-of-arrays describes dependencies between
+      # middlewares: the first item in each list depends on the
+      # remaining items (and therefore must occur later in the
+      # middleware stack).
+
+      dependencies = [
+        # Logger needs a fully "corrected" request environment
+        %w(Rails::Rack::Logger Rack::MethodOverride ActionDispatch::RequestId ActionDispatch::RemoteIp),
+
+        # Serving public/ doesn't invoke user code, so it should skip
+        # locks etc
+        %w(ActionDispatch::Executor ActionDispatch::Static),
+
+        # Errors during reload must be reported
+        %w(ActionDispatch::Reloader ActionDispatch::ShowExceptions ActionDispatch::DebugExceptions),
+
+        # Outright dependencies
+        %w(ActionDispatch::Static Rack::Sendfile),
+        %w(ActionDispatch::Flash ActionDispatch::Session::CookieStore),
+        %w(ActionDispatch::Session::CookieStore ActionDispatch::Cookies),
+      ]
+
+      require "tsort"
+      sorted = TSort.tsort((middleware | dependencies.flatten).method(:each),
+                           lambda { |n, &b| dependencies.each { |m, *ds| ds.each(&b) if m == n } })
+      assert_equal sorted, middleware
+    end
+
     test "Rack::Cache is not included by default" do
       boot!
 
@@ -246,7 +277,7 @@ module ApplicationTests
       get "/", {}, "HTTP_IF_NONE_MATCH" => etag
       assert_equal 304, last_response.status
       assert_equal "", last_response.body
-      assert_equal nil, last_response.headers["Content-Type"]
+      assert_nil last_response.headers["Content-Type"]
       assert_equal "max-age=0, private, must-revalidate", last_response.headers["Cache-Control"]
       assert_equal etag, last_response.headers["Etag"]
 
@@ -255,7 +286,7 @@ module ApplicationTests
       assert_equal "", last_response.body
       assert_equal "text/plain; charset=utf-8", last_response.headers["Content-Type"]
       assert_equal "no-cache", last_response.headers["Cache-Control"]
-      assert_equal nil, last_response.headers["Etag"]
+      assert_nil last_response.headers["Etag"]
     end
 
     test "ORIGINAL_FULLPATH is passed to env" do