diff --git a/docker-compose.yml b/docker-compose.yml
index 1c98169d242..c7c9ad81806 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -123,6 +123,13 @@ services:
     networks:
       - testing
 
+  hocuspocus-test:
+    image: openproject/hocuspocus:latest
+    environment:
+      SECRET: secret12345
+    networks:
+      - testing
+
   frontend-test:
     build:
       <<: *frontend-build
@@ -157,8 +164,11 @@ services:
         condition: service_healthy
       cuprite-chrome:
         condition: service_started
+      hocuspocus-test:
+        condition: service_started
     environment:
       RAILS_ENV: test
+      OPENPROJECT_TESTING_WITH_DOCKER: "true"
       OPENPROJECT_RAILS__RELATIVE__URL__ROOT: "${OPENPROJECT_RAILS__RELATIVE__URL__ROOT:-}"
       DATABASE_URL: postgresql://openproject:openproject@db-test/openproject
       DATABASE_CLEANER_ALLOW_REMOTE_DATABASE_URL: "true"
diff --git a/modules/documents/spec/features/real_time_collaboration_spec.rb b/modules/documents/spec/features/real_time_collaboration_spec.rb
new file mode 100644
index 00000000000..e75b1706271
--- /dev/null
+++ b/modules/documents/spec/features/real_time_collaboration_spec.rb
@@ -0,0 +1,104 @@
+# frozen_string_literal: true
+
+#-- copyright
+# OpenProject is an open source project management software.
+# Copyright (C) the OpenProject GmbH
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License version 3.
+#
+# OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
+# Copyright (C) 2006-2013 Jean-Philippe Lang
+# Copyright (C) 2010-2013 the ChiliProject Team
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+#
+# See COPYRIGHT and LICENSE files for more details.
+#++
+
+require "spec_helper"
+require_module_spec_helper
+
+RSpec.describe "Real-time collaboration with Hocuspocus for documents",
+               :js,
+               :selenium do
+  let(:editor) { FormFields::Primerized::BlockNoteEditorInput.new }
+  let(:admin) { create(:admin, firstname: "Armin", lastname: "Admin") }
+  let(:member_role) { create(:existing_project_role, permissions: [:view_documents]) }
+  let(:readonly_user) { create(:user, member_with_roles: { project => member_role }, firstname: "Rita", lastname: "Readonly") }
+  let(:project) { create(:project) }
+  let(:document) { create(:document, :collaborative, project:) }
+
+  before do
+    # These tests require a running Hocuspocus server. You can either run one
+    # locally or use the docker test setup.
+    host = ENV["OPENPROJECT_TESTING_WITH_DOCKER"] == "true" ? "hocuspocus-test" : "127.0.0.1"
+    port = 1234
+    Setting.collaborative_editing_hocuspocus_url = "ws://#{host}:#{port}"
+    Setting.collaborative_editing_hocuspocus_secret = "secret12345"
+
+    begin
+      TCPSocket.new(host, port).close
+    rescue Errno::ECONNREFUSED, Errno::EHOSTUNREACH, SocketError => e
+      raise("Hocuspocus server not reachable at #{host}:#{port} - #{e.message}")
+    end
+  end
+
+  context "with write permission" do
+    before do
+      login_as(admin)
+    end
+
+    it "shows the editor" do
+      visit document_path(document)
+      expect(page).to have_test_selector("blocknote-document-description")
+      expect(page).to have_no_content("Armin Admin")
+      page.find_link("1 active editor").click
+      expect(page).to have_content("Armin Admin")
+    end
+
+    it "renders a collaborative document and saves changes to the database" do
+      visit document_path(document)
+      expect(document.content_binary).to be_nil
+      expect(page).to have_test_selector("blocknote-document-description")
+
+      editor.fill_in("Hello Hocuspocus")
+      wait_for { document.reload.content_binary }.to be_present
+      expect(document.description).to eq("Hello Hocuspocus\n")
+    end
+  end
+
+  context "with readonly permission" do
+    before do
+      login_as(readonly_user)
+    end
+
+    it "shows the editor but does not accept writes" do
+      # rubocop:disable Layout/LineLength
+      binary = "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"
+      # rubocop:enable Layout/LineLength
+      document.update!(content_binary: binary, description: "Hello Hocuspocus\n")
+      visit document_path(document)
+      expect(page).to have_test_selector("blocknote-document-description")
+      wait_for { editor.content }.to have_content("Hello Hocuspocus")
+      editor.fill_in("Nothing changes")
+      # Hocuspocus takes some time before saving. It's hard to wait for
+      # something to not change, so this sleeps, although it's bad to do that in tests.
+      sleep 5 # rubocop:disable OpenProject/NoSleepInFeatureSpecs
+      expect(document.reload.content_binary).to eql(binary) # nothing changed
+      expect(document.description).to eq("Hello Hocuspocus\n")
+    end
+  end
+end