Add test against plugin

.github/hello_world/README.rdoc

@@ -0,0 +1,3 @@
+= hello_world
+
+Description goes here

.github/hello_world/app/models/hello.rb

@@ -0,0 +1,2 @@
+class Hello < ApplicationRecord
+end

.github/hello_world/config/locales/en.yml

@@ -0,0 +1,3 @@
+# English strings go here for Rails i18n
+en:
+  # my_label: "My label"

.github/hello_world/config/routes.rb

@@ -0,0 +1,2 @@
+# Plugin's routes
+# See: http://guides.rubyonrails.org/routing.html

.github/hello_world/db/migrate/20240518044930_create_hellos.rb

@@ -0,0 +1,7 @@
+class CreateHellos < ActiveRecord::Migration[7.1]
+  def change
+    create_table :hellos do |t|
+      t.string :world
+    end
+  end
+end

.github/hello_world/init.rb

@@ -0,0 +1,8 @@
+Redmine::Plugin.register :hello_world do
+  name 'Hello World'
+  author 'Author name'
+  description 'This is a plugin for Redmine'
+  version '0.0.1'
+  url 'http://example.com/path/to/plugin'
+  author_url 'http://example.com/about'
+end

.github/hello_world/test/test_helper.rb

@@ -0,0 +1,2 @@
+# Load the Redmine helper
+require_relative '../../../test/test_helper'

.github/hello_world/test/unit/hello_test.rb

@@ -0,0 +1,8 @@
+require_relative '../test_helper'
+
+class HelloTest < ActiveSupport::TestCase
+  def test_world
+    Hello.create world: "Redmine"
+    assert_equal "Redmine", Hello.first.world
+  end
+end

.github/workflows/build.yml

@@ -53,14 +53,22 @@ jobs:
         database: ${{ matrix.redmine-database }}
         ruby-version: ${{ matrix.ruby-version }}
 
+    - name: Install a plugin for testing
+      run: |
+        cp -R ../.github/hello_world plugins/
+        bin/rails redmine:plugins:migrate
+      working-directory: ${{ env.REDMINE_SRC }}
+
     - run: |
         about=$(bin/rails r "require 'redmine/version'; puts Redmine::Info.environment")
         echo "$about"
         echo "$about" | grep "${{ matrix.expected-about-db-adapter }}"
         echo "$about" | grep "${{ matrix.expected-about-redmine-version }}"
+        echo "$about" | grep "Hello World"
       working-directory: ${{ env.REDMINE_SRC }}
 
     - run: |
         bin/rails test test/unit/news_test.rb
         bin/rails test test/system/my_page_test.rb
+        bin/rails redmine:plugins:test
       working-directory: ${{ env.REDMINE_SRC }}