Test: Disable Open4 calls, add mock_system_command helper

lib/errors.rb

@@ -0,0 +1 @@
+class SystemCommandNotAllowedError < StandardError; end

test/test_helper.rb

@@ -3,6 +3,7 @@ require_relative "../config/environment"
 require "rails/test_help"
 
 require "minitest/mock"
+require_relative "test_mocks_helper"
 
 class ActiveSupport::TestCase
   # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
@@ -12,9 +13,12 @@ class ActiveSupport::TestCase
   Warden.test_mode!
 
   # Add more helper methods to be used by all tests here...
+  include ActiveJob::TestHelper
   include FactoryBot::Syntax::Methods
+  include TestMocksHelper
 end
 
+# Capybara configuration
 Capybara.register_driver :headless_chrome do |app|
   capabilities = Selenium::WebDriver::Remote::Capabilities.chrome(
     "chromeOptions" => { args: %w[headless disable-gpu] + ["window-size=1280,800"] },
@@ -23,3 +27,21 @@ Capybara.register_driver :headless_chrome do |app|
 end
 Capybara.save_path = Rails.root.join("tmp/capybara")
 Capybara.javascript_driver = :headless_chrome
+
+# Disable Open4 real system calls
+require "open4"
+require "errors"
+module Open4
+  def popen4(*)
+    fail SystemCommandNotAllowedError,
+      "Real Open4 calls are disabled in test env. Use mock_system_command helper instead."
+  end
+  alias open4 popen4
+  alias pfork4 popen4
+  alias popen4ext popen4
+
+  module_function :open4
+  module_function :popen4
+  module_function :pfork4
+  module_function :popen4ext
+end

test/test_mocks_helper.rb

@@ -0,0 +1,29 @@
+require "system_command"
+
+module TestMocksHelper
+  # rubocop:disable Metrics/MethodLength
+  def mock_system_command(program, args, exit_status: 0, stdout: "", stderr: "")
+    syscmd = "#{program} #{Array.wrap(args).join(' ')}"
+    result = SystemCommandResult.new(syscmd, exit_status, stdout, stderr)
+
+    mock = Minitest::Mock.new
+    mock.expect :execute, result
+
+    fussy = lambda { |actual_program, actual_args, _logger|
+      assert_equal program, actual_program,
+       "SystemCommand was not initialized with the expected program name"
+
+      assert_equal args, actual_args,
+       "SystemCommand was not initialized with the expected arguments"
+
+      mock
+    }
+
+    SystemCommand.stub :new, fussy do
+      yield
+    end
+
+    mock.verify
+  end
+  # rubocop:enable Metrics/MethodLength
+end