Devcontainers: Introduce SystemTestCase#served_by

When working in a devcontainer, for system tests we need to manually set the host and port serving the application. Let's introduce a method for this, so we don't have to expose the implementation details of Capybara to the developer.

Co-authored-by: Rafael Mendonça França <rafael@franca.dev>

actionpack/lib/action_dispatch/system_test_case.rb

@@ -161,6 +161,14 @@ def self.driven_by(driver, using: :chrome, screen_size: [1400, 1400], options: {
       self.driver = SystemTesting::Driver.new(driver, **driver_options, &capabilities)
     end
 
+    # Configuration for the System Test application server
+    #
+    # By default this is localhost. This method allows the host and port to be specified manually.
+    def self.served_by(host:, port:)
+      Capybara.server_host = host
+      Capybara.server_port = port
+    end
+
     private
       def url_helpers
         @url_helpers ||=

railties/CHANGELOG.md

@@ -1,3 +1,15 @@
+*   Introduce `SystemTestCase#served_by` for configuring the System Test application server
+
+    By default this is localhost. This method allows the host and port to be specified manually.
+
+    ```ruby
+    class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
+      served_by host: "testserver", port: 45678
+    end
+    ```
+
+    *Andrew Novoselac & Rafael Mendonça França*
+
 *   Ensure logger tags configured with `config.log_tags` are still active in `request.action_dispatch` handlers
 
     *KJ Tsanaktsidis*