Add a test for install git gems will only clone once

test/installer_test.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+require "gel/installer"
+
+class InstallerTest < Minitest::Test
+  def test_install_git_gems_only_checkout_once
+    Dir.mktmpdir do |dir|
+      remote = "https://github.com/rails/rails.git"
+      revision = "d56d2e740612717334840b0d0ea979e1ca7cf5b1"
+      names = ["actioncable", "actionmailbox"]
+      store = Gel::Store.new(dir)
+      installer = Gel::Installer.new(store)
+      fake_download_pool = Minitest::Mock.new
+      installer.instance_variable_set(
+        :@download_pool,
+        fake_download_pool
+      )
+      fake_download_pool.expect(:queue, true) do |argument|
+        argument == "actioncable"
+      end
+
+      names.each do |name|
+        installer.load_git_gem(remote, revision, "actioncable")
+      end
+    end
+  end
+end