Add tests for env fallback in normalize publish script

Agent-Logs-Url: https://github.com/rails/devcontainer/sessions/23db5954-a602-4ea7-94c3-bd7a0be7c1f5

Co-authored-by: rafaelfranca <47848+rafaelfranca@users.noreply.github.com>

Author: Copilot

test/commands/normalize_publish_inputs_script_test.rb

@@ -0,0 +1,78 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require "minitest/autorun"
+require "open3"
+require "rbconfig"
+require "tempfile"
+
+class NormalizePublishInputsScriptTest < Minitest::Test
+  def test_reads_values_from_env_when_args_are_omitted
+    output = Tempfile.new("github-output")
+
+    status = run_script(
+      {
+        "RUBY_VERSIONS" => "3.3.1,3.2.4",
+        "IMAGE_VERSIONS" => "ruby-1.1.0",
+        "REPOSITORY" => "rails/devcontainer",
+        "GITHUB_OUTPUT" => output.path
+      }
+    )
+
+    assert status.success?
+    assert_equal '["3.3.1","3.2.4"]', parse_output(output.path).fetch("ruby_versions_json")
+  ensure
+    output&.close!
+  end
+
+  def test_prefers_args_over_env_values
+    output = Tempfile.new("github-output")
+
+    status = run_script(
+      {
+        "RUBY_VERSIONS" => "3.0.0",
+        "IMAGE_VERSIONS" => "ruby-1.1.0",
+        "REPOSITORY" => "rails/devcontainer",
+        "GITHUB_OUTPUT" => output.path
+      },
+      "--ruby-versions", "3.3.1",
+      "--image-versions", "ruby-1.2.0",
+      "--repository", "rails/devcontainer"
+    )
+
+    assert status.success?
+    result = parse_output(output.path)
+    assert_equal '["3.3.1"]', result.fetch("ruby_versions_json")
+    assert_equal '["ruby-1.2.0"]', result.fetch("image_versions_json")
+  ensure
+    output&.close!
+  end
+
+  private
+
+  def run_script(env, *args)
+    _stdout, _stderr, status = Open3.capture3(
+      env,
+      RbConfig.ruby,
+      script_path,
+      *args,
+      chdir: repo_root
+    )
+    status
+  end
+
+  def parse_output(path)
+    File.read(path).lines.to_h do |line|
+      key, value = line.strip.split("=", 2)
+      [key, value]
+    end
+  end
+
+  def script_path
+    File.join(repo_root, "bin/normalize-publish-inputs")
+  end
+
+  def repo_root
+    File.expand_path("../..", __dir__)
+  end
+end