Tests won't work with string interpolation: _parse_test_output fails

[teddyhwang]

Similar to #2, any test cases that have string interpolation (due to being in a loop) fails to parse.

Example test:

# typed: false
# frozen_string_literal: true

require "test_helper"

class ErbImplementationTest < ActiveSupport::TestCase
  ERB_GLOB = Rails.root.join(
    "app", "views", "**", "{*.htm,*.html,*.htm.erb,*.html.erb,*.html+*.erb}"
  )

  Dir[ERB_GLOB].each do |filename|
    pathname = Pathname.new(filename).relative_path_from(Rails.root)
    test "html errors in #{pathname}" do
      data = File.read(filename)
      BetterHtml::BetterErb::ErubiImplementation.new(data).validate!
    end
  end
end