```ruby
# encoding: utf-8

Gem::Specification.new do |s|
  s.name        = 'mocoso'
  s.version     = '1.2.0'
  s.summary     = 'A simple stub & mock library'
  s.description = s.summary
  s.authors     = ['Francesco Rodríguez']
  s.email       = ['lrodriguezsanc@gmail.com']
  s.homepage    = 'https://github.com/frodsan/mocoso'
  s.license     = 'MIT'

  s.files = Dir[
    'LICENSE',
    'README.md',
    'lib/**/*.rb',
    '*.gemspec',
    'test/*.*'
  ]

  s.add_development_dependency 'cutest'
end
```

Use double quotes in gemspec.
user
```ruby
Gem::Specification.new do |s|
  s.name        = "mocoso"
  s.version     = "1.2.0"
  s.summary     = "A simple stub & mock library"
  s.description = s.summary
  s.authors     = ["Francesco Rodríguez"]
  s.email       = ["lrodriguezsanc@gmail.com"]
  s.homepage    = "https://github.com/frodsan/mocoso"
  s.license     = "MIT"

  s.files = Dir[
    "LICENSE",
    "README.md",
    "lib/**/*.rb",
    "*.gemspec",
    "test/*.*"
  ]

  s.add_development_dependency "cutest"
end
```
assistant