Artifice allows you to replace the Net::HTTP subsystem of Ruby with an equivalent that routes all requests to a Rack application.

Rails Long Term Support

Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)

• Prevents you from data breaches and liability risks
• Upgrade at your own pace
• Works with modern Rubies

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You can use Sinatra, raw Rack, or even Rails as your application, allowing you to build up an equivalent to the remote service you are mocking out using familiar and convenient tools to route requests and build up responses.