JSON Schema matchers for RSpec
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README.md

JSON::SchemaMatchers

This gem adds matchers to rspec for validating JSON strings against JSON schemas.

JSON schemas are great for ensuring that changes in applications don't break their integrations, without having to write complex integration tests or run many application environments on your development machine.

Installation

Add this line to your application's Gemfile:

gem 'json-schema-rspec'

And then execute:

$ bundle

Or install it yourself as:

$ gem install json-schema-rspec

Usage

In your spec_helper.rb:

config.include JSON::SchemaMatchers

#schema file
config.json_schemas[:my_schema] = "path/to/schema.json"
#inline
config.json_schemas[:inline_schema] = '{"type": "string"}'

You can then write tests such as:

#passing spec
expect('"hello world"').to match_json_schema(:inline_schema)

#failing spec
expect('[1, 2, 3]').to match_json_schema(:inline_schema)

It also works as an argument matcher:

expect(some_object).to receive(:some_method).with(object_matching_schema(:inline_schema))

The argument matcher will match anything that the underlying JSON-Schema validator knows how to validate, so if you want to limit your argument to a certain class, you'll need to add a compound matcher for that.

expect(some_object).to receive(:some_method)
  .with(an_instance_of(String).and(object_matching_schema(:inline_schema)))

Strict schema validation

If you wish to use strict schema validation you can do so by passing an additional argument to the matcher. strict validation can be useful if you want to ensure there are no additional properties in the JSON than those explicitly defined in your schema

expect(response.body).to match_json_schema(:my_schema, strict: true)

Schema in a file

You can also use rails path utilities such as Rails.root.join("spec/support/schemas/my_business_object.schema.json").to_s when defining schema locations. This gem is backed by the json-schema gem, so whatever that validator accepts for paths should work.

Inline Schema

While not recommended due to their size, inline schemas are supported. This may be useful for very simple schemas or if schemas are generated dynamically from some other process.

Remote Schemas

Reading a schema from a web address is also supported, but with some limitations. Under the covers, the json-schema gem uses simple ruby open and read methods, so tread lightly. Accessing resources that are restricted by even simple HTTP auth will probably not work.

One work-around here would be to read your schema using some other mechanism (such as the RestClient gem) and passing it to config.json_schemas as an inline schema.

config.json_schemas[:remote_protected_object] = RestClient.get("http://username:password@artifacts.sharethrough.com/object.schema.json")

Contributing

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request