Add a test to confirm command visibility when hooked on cli_init.

Author: Jeremy Ward

features/command.feature

@@ -1666,3 +1666,35 @@ Feature: WP-CLI Commands
       """
       core custom-subcommand
       """
+
+  Scenario: An activated plugin should successfully trigger custom commands on the cli_init action.
+    Given a WP installation
+    And a wp-content/plugins/custom-command/custom-cmd.php file:
+      """
+      <?php
+      // Plugin Name: Custom Command
+
+      add_action( 'cli_init', function() {
+        require_once plugin_dir_path( __FILE__ ) . '/class-custom-command.php';
+        $command = new Custom_Command();
+        WP_CLI::add_command( 'custom', array( $command, 'do_custom_command' ) );
+      } );
+      """
+    And a wp-content/plugins/custom-command/class-custom-command.php file:
+    """
+    <?php
+    class Custom_Command extends WP_CLI_Command {
+      /**
+      * Tell the whole world!
+      */
+      public function do_custom_command() {
+        WP_CLI::success( "This command doesn't really do much, does it?" );
+      }
+    }
+    """
+    And I run `wp plugin activate custom-command`
+    When I run `wp custom --help`
+    Then STDOUT should contain:
+    """
+    wp custom
+    """