Duplicated dev dependencies

[16]

In gemspec, remove dev dependencies since they are already declared in the Gemfile ? Or removing them from Gemfile ? See bundler and rubygems documentation

[16]

Based on my recent discussions, I realised that not everyone uses Bundler to develop their Ruby gems. Some developers even have a strong aversion to using it. Whether you like it or not, a few years from now Bundler may not be the tool that everyone uses to install their dependencies. But, you want to be able to continue building your gem. Because of this, I tend to include the most essential development dependencies necessary to test and build a gem.
— Writing a Ruby Gem Specification