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

# 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

--- 
+++ 
@@ -1,22 +1,20 @@
-# encoding: utf-8
-
 Gem::Specification.new do |s|
-  s.name        = 'mocoso'
-  s.version     = '1.2.0'
-  s.summary     = 'A simple stub & mock library'
+  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.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/*.*'
+    "LICENSE",
+    "README.md",
+    "lib/**/*.rb",
+    "*.gemspec",
+    "test/*.*"
   ]
 
-  s.add_development_dependency 'cutest'
+  s.add_development_dependency "cutest"
 end
Use double quotes in gemspec.
