Update system test runner docs

It wasn't clear that system tests don't run with the rest of the test
suite and are part of a separate command.

This documents the `test:system` command as well as update the Rails
runner help documentation to make it clearer that system tests are run
via their own command by default.

2 files changed, 10 insertions, 8 deletions

diff --git a/railties/lib/rails/commands/help/USAGE b/railties/lib/rails/commands/help/USAGE
index c5f8ab72bb..8eb98319d2 100644
--- a/railties/lib/rails/commands/help/USAGE
+++ b/railties/lib/rails/commands/help/USAGE
@@ -1,13 +1,14 @@
 The most common rails commands are:
- generate    Generate new code (short-cut alias: "g")
- console     Start the Rails console (short-cut alias: "c")
- server      Start the Rails server (short-cut alias: "s")
- test        Run tests (short-cut alias: "t")
- dbconsole   Start a console for the database specified in config/database.yml
-             (short-cut alias: "db")
+ generate     Generate new code (short-cut alias: "g")
+ console      Start the Rails console (short-cut alias: "c")
+ server       Start the Rails server (short-cut alias: "s")
+ test         Run tests except system tests (short-cut alias: "t")
+ test:system  Run system tests
+ dbconsole    Start a console for the database specified in config/database.yml
+              (short-cut alias: "db")
 <% unless engine? %>
- new         Create a new Rails application. "rails new my_app" creates a
-             new application called MyApp in "./my_app"
+ new          Create a new Rails application. "rails new my_app" creates a
+              new application called MyApp in "./my_app"
 <% end %>
 
 All commands can be run with -h (or --help) for more information.
diff --git a/railties/lib/rails/test_unit/testing.rake b/railties/lib/rails/test_unit/testing.rake
index ef19bd7626..33408081f1 100644
--- a/railties/lib/rails/test_unit/testing.rake
+++ b/railties/lib/rails/test_unit/testing.rake
@@ -48,6 +48,7 @@ namespace :test do
     Minitest.rake_run(["test/controllers", "test/mailers", "test/functional"])
   end
 
+  desc "Run system tests only"
   task system: "test:prepare" do
     $: << "test"
     Minitest.rake_run(["test/system"])