Add Guard to run specs on save

This aims to make TDD practice easier.

---

Changelog: chore

Author: jvortmann

Guardfile

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+logger level: :error
+
+guard :rspec, cmd: "bundle exec rspec --format #{ENV.fetch("FORMAT", "documentation")}" do
+  require "guard/rspec/dsl"
+  dsl = Guard::RSpec::Dsl.new(self)
+
+  # Ruby files
+  ruby = dsl.ruby
+  dsl.watch_spec_files_for(ruby.lib_files)
+  watch(%r{^lib/(.+)\.rb}) { |m| "spec/#{m[1]}_spec.rb" }
+
+  # RSpec files
+  rspec = dsl.rspec
+  watch(rspec.spec_helper) { rspec.spec_dir }
+  watch(rspec.spec_support) { rspec.spec_dir }
+  watch(rspec.spec_files)
+end

rdkafka.gemspec

@@ -25,4 +25,6 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency 'rspec', '~> 3.5'
   gem.add_development_dependency 'rake'
   gem.add_development_dependency 'simplecov'
+  gem.add_development_dependency 'guard'
+  gem.add_development_dependency 'guard-rspec'
 end