Tests for bun

Ensures:

1. The bun config file is copied
2. The bun command is used as a build script
3. The Procfile.dev is copied / modified

test/installer/bun_test.rb

@@ -0,0 +1,36 @@
+require "json"
+require "test_helper"
+
+class BunInstallerTest < ActiveSupport::TestCase
+  include RailsAppHelpers
+
+  test "installer for bun" do
+    with_new_rails_app do
+      _out, _err = run_command("bin/rails", "javascript:install:bun")
+
+      assert_match "js: bun run build --watch", File.read("Procfile.dev")
+
+      assert_equal File.read("#{__dir__}/../../lib/install/bun/bun.config.js"), File.read("bun.config.js")
+
+      JSON.parse(File.read("package.json")).tap do |package|
+        assert_equal("bun bun.config.js", package["scripts"]["build"])
+      end
+
+      if sprockets?
+        assert_match "//= link_tree ../builds", File.read("app/assets/config/manifest.js")
+      end
+    end
+  end
+
+  test "installer with pre-existing Procfile" do
+    with_new_rails_app do
+      File.write("Procfile.dev", "pre: existing\n")
+      _out, _err = run_command("bin/rails", "javascript:install:bun")
+
+      assert_equal <<~YAML, File.read("Procfile.dev")
+        pre: existing
+        js: bun run build --watch
+      YAML
+    end
+  end
+end