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Inferno Documentation

Introduction to Inferno

Inferno is an application framework for creating, executing, and sharing conformance tests for FHIR APIs. Inferno tests are packaged within portable test applications called Inferno Test Kits. Test Kits are tailored to test specific FHIR-enabled data exchange use cases, typically described within one or more FHIR Implementation Guides (IGs).

For example:

If you would like to learn how to run or deploy an existing Inferno Test Kit, please visit the Using Test Kits documentation.

A Test Kit is a standalone Ruby application that can be run on an end user’s machine, on a shared private host behind a firewall, or on a shared public host such as It is built with the Inferno Core gem, which provides several useful features for a FHIR testing application, including:

  • The Inferno DSL - A domain specific language (DSL) for authoring FHIR API tests that includes a FHIR client, native Ruby classes for FHIR, and FHIR instance validators
  • API, Web and CLI Interfaces - Multiple interface options for executing tests and retrieving results
  • Test Reuse - Methods for reusing tests within a project or from other projects

Inferno Core provides common utilities for FHIR-based testing, but tests are not limited to what is provided by Inferno Core.

Inferno’s design reflects the flexibility provided by the base FHIR specification. FHIR is a platform specification that is intended to provide support across the whole healthcare process, so it relies on IGs to provide enough specificity to enable meaningful interoperability between actors for a given data exchange use case. FHIR IGs will typically describe how to use relevant portions of the FHIR specification for its use case while also providing additional rules not described in FHIR. There are no limits to what these additional rules may include; for example, other standards can be required, such as OAuth or QR Codes for Vaccination Credentials, as part of their conformance criteria.

Creating a test system that is flexible enough to test any arbitrary conformance criteria introduced in an IG is challenging. Inferno accomplishes this by providing test authors with a full-featured Ruby programming environment to define and run tests. It also allows the use of the open-source third-party libraries provided by Ruby. This makes Inferno well-suited for testing IGs that:

  • include additional standards beyond FHIR,
  • have large specifications that could benefit from Ruby’s meta-programming capabilities to ease maintenance burden,
  • or require complex logic to thoroughly validate API responses.

While Ruby is sufficient for most testing needs, test developers may want to include components that are not defined in Ruby. Inferno Test Kits can include these non-Ruby services as needed, and by default provides a Docker Compose configuration to run and integrate with these services from within Inferno’s testing DSL.

Main Inferno Repositories

  • Inferno Core - The Inferno Ruby library. This repository that contains the code for defining and running tests and the command line and web interfaces. This is the repository to use if you want to investigate or make changes to the internals of Inferno.
  • Inferno Template - A template for test writers. This is the repository to use if you want to write your own set of tests with Inferno.
  • FHIR Validator Wrapper - A simple web wrapper around the official HL7 FHIR validation library. Inferno relies on this service to validate FHIR resources.

Documentation Resources

Inferno Test Kits

Visit the Community Page to view all available Test Kits.