Split up railties/test/command/application_test.rb

Follow-up to rails#47208.

Prior to rails#47208, `Rails::Command::ApplicationTest` appears to have been
specifically intended to test `Rails::Command::ApplicationCommand`.
Therefore, this commit extracts the tests that were added by rails#47208 out
from `railties/test/command/application_test.rb` into
`railties/test/command/help_integration_test.rb`, and moves
`application_test.rb` from `railties/test/command` to
`railties/test/commands` (with the rest of the command-specific tests).

Author: jonathanhefner

railties/test/command/application_test.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+require "rails/command"
+
+class Rails::Command::HelpIntegrationTest < ActiveSupport::TestCase
+  setup :build_app
+  teardown :teardown_app
+
+  test "prints helpful error on unrecognized command" do
+    output = rails "vershen", allow_failure: true
+
+    assert_match %(Unrecognized command "vershen"), output
+    assert_match "Did you mean?  version", output
+  end
+
+  test "prints help via `X:help` command when running `X` and `X:X` command is not defined" do
+    help = rails "dev:help"
+    output = rails "dev", allow_failure: true
+
+    assert_equal help, output
+  end
+end

railties/test/command/help_integration_test.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "rails/command"
+
+class Rails::Command::ApplicationTest < ActiveSupport::TestCase
+  test "rails new without path prints help" do
+    output = run_application_command "new"
+
+    # Doesn't include the default thor error message:
+    assert_not output.start_with?("No value provided for required arguments")
+
+    # Includes contents of ~/railties/lib/rails/generators/rails/app/USAGE:
+    assert output.include?("The `rails new` command creates a new Rails application with a default
+    directory structure and configuration at the path you specify.")
+  end
+
+  private
+    def run_application_command(*args)
+      capture(:stdout) { Rails::Command.invoke(:application, args) }
+    end
+end