Make sure debug is available in tests (#200)

This is just a small quality of life thing that makes sure the debug gem
is available when running tests.

I tested this by putting binding.b in a test file and running
bin/test-unit. Before this change my debugger wasn't caught but now it
is!

Author: flavorjones

Gemfile

@@ -4,11 +4,11 @@ source "https://rubygems.org"
 
 gemspec
 
-group :development do
+group :development, :test do
   gem "rails", github: "rails/rails", branch: "main"
   gem "sqlite3", "2.7.4"
   gem "debug", "1.11.0"
-  gem "minitest-parallel_fork", "2.1.0"
+  gem "minitest-parallel_fork", "2.1.0", require: false
 end
 
 group :rubocop do