Test against multiple Ruby versions

.travis.yml

@@ -4,7 +4,9 @@ dist: trusty
 language: ruby
 
 rvm:
-  - 2.5.0
+  - 2.3.7
+  - 2.4.4
+  - 2.5.1
 
 gemfile:
   - gemfiles/spree_3_5.gemfile
@@ -21,6 +23,7 @@ deploy:
   on:
     tags: true
     repo: mollie/spree-mollie-gateway
+    rvm: 2.5.1
   api_key:
     secure: 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
 

spree_mollie_gateway.gemspec

@@ -3,16 +3,16 @@ $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'spree_mollie_gateway/version'
 
 Gem::Specification.new do |spec|
-  spec.name          = 'spree_mollie_gateway'
-  spec.version       = SpreeMollieGateway::VERSION
-  spec.authors       = ['Vernon de Goede']
-  spec.email         = ['vernon@mollie.com']
+  spec.name = 'spree_mollie_gateway'
+  spec.version = SpreeMollieGateway::VERSION
+  spec.authors = ['Vernon de Goede']
+  spec.email = ['vernon@mollie.com']
 
-  spec.summary       = 'Mollie payments for Spree Commerce.'
-  spec.description   = 'Mollie payment gateway for Spree Commerce.'
-  spec.homepage      = 'https://www.mollie.com'
+  spec.summary = 'Mollie payments for Spree Commerce.'
+  spec.description = 'Mollie payment gateway for Spree Commerce.'
+  spec.homepage = 'https://www.mollie.com'
 
-  spec.licenses      = ['BSD']
+  spec.licenses = ['BSD']
 
   # Prevent pushing this gem to RubyGems.org. To allow pushes either set the 'allowed_push_host'
   # to allow pushing to a single host or delete this section to allow pushing to any host.
@@ -26,9 +26,10 @@ Gem::Specification.new do |spec|
   spec.files = `git ls-files -z`.split("\x0").reject do |f|
     f.match(%r{^(test|spec|features)/})
   end
-  spec.bindir        = 'exe'
-  spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
+  spec.bindir = 'exe'
+  spec.executables = spec.files.grep(%r{^exe/}) {|f| File.basename(f)}
   spec.require_paths = ['lib']
+  spec.required_ruby_version = '>= 2.3.8'
 
   spree_version = '>= 3.1.0', '< 5.0'
   spec.add_dependency 'spree_backend', spree_version