JsonMatchers

Validate the JSON returned by your Rails JSON APIs

Add this line to your application's Gemfile:

group :test do
  gem "json_matchers"
end

And then execute:

$ bundle

Or install it yourself as:

$ gem install json_matchers

Inspired by Validating JSON Schemas with an RSpec Matcher.

First, configure it in your test suite's helper file:

spec/spec_helper.rb

require "json_matchers/rspec"

JsonMatchers.schema_root = "spec/support/api/schemas"

test/test_helper.rb

require "minitest/autorun"
require "json_matchers/minitest/assertions"

JsonMatchers.schema_root = "test/support/api/schemas"

Minitest::Test.include(JsonMatchers::Minitest::Assertions)

Declare your JSON Schema in the schema directory.

spec/support/api/schemas/location.json or test/support/api/schemas/location.json:

Define your JSON Schema in the schema directory.

{
  "id": "https://json-schema.org/geo",
  "$schema": "https://json-schema.org/draft-06/schema#",
  "description": "A geographical coordinate",
  "type": "object",
  "properties": {
    "latitude": {
      "type": "number"
    },
    "longitude": {
      "type": "number"
    }
  }
}

Validate a JSON response, a Hash, or a String against a JSON Schema with match_json_schema:

spec/requests/locations_spec.rb

describe "GET /locations" do
  it "returns Locations" do
    get locations_path, format: :json

    expect(response.status).to eq 200
    expect(response).to match_json_schema("locations")
  end
end

Validate a JSON response, a Hash, or a String against a JSON Schema with assert_matches_json_schema:

test/integration/locations_test.rb

def test_GET_posts_returns_Locations
  get locations_path, format: :json

  assert_equal response.status, 200
  assert_matches_json_schema response, "locations"
end

To re-use other schema definitions, include $ref keys that refer to their definitions.

First, declare the singular version of your schema.

spec/support/api/schemas/user.json:

{
  "id": "file:/user.json#",
  "type": "object",
  "required": ["id"],
  "properties": {
    "id": { "type": "integer" },
    "name": { "type": "string" },
    "address": { "type": "string" },
  },
}

Then, when you declare your collection schema, reference your singular schemas.

spec/support/api/schemas/users/index.json:

{
  "id": "file:/users/index.json#",
  "type": "object",
  "definitions": {
    "users": {
      "description": "A collection of users",
      "example": [{ "id": "1" }],
      "type": "array",
      "items": {
        "$ref": "file:/user.json#"
      },
    },
  },
  "required": ["users"],
  "properties": {
    "users": {
      "$ref": "#/definitions/users"
    }
  },
}

NOTE: $ref resolves paths relative to the schema in question.

In this case "user.json" and "users/index.json" are resolved relative to "spec/support/api/schemas" or "test/support/api/schemas".

To learn more about $ref, check out Understanding JSON Schema Structuring.

Nesting a schema within a subdirectory is also supported:

spec/support/api/schemas/api/v1/location.json:

{
  "id": "https://json-schema.org/geo",
  "$schema": "https://json-schema.org/draft-06/schema#",
  "description": "A geographical coordinate",
  "type": "object",
  "properties": {
    "latitude": {
      "type": "number"
    },
    "longitude": {
      "type": "number"
    }
  }
}

spec/requests/api/v1/locations_spec.rb:

describe "GET api/v1/locations" do
  it "returns Locations" do
    get locations_path, format: :json

    expect(response.status).to eq 200
    expect(response).to match_json_schema("api/v1/location")
  end
end

By default, the schema directory is spec/support/api/schemas.

This can be configured via JsonMatchers.schema_root.

# spec/support/json_matchers.rb

JsonMatchers.schema_root = "docs/api/schemas"

Calls to match_json_schema and match_response_schema no longer accept options, and JsonMatchers.configure has been removed.

Please see CONTRIBUTING.

json_matchers was inspired by Validating JSON Schemas with an RSpec Matcher by Laila Winner.

json_matchers is maintained by Sean Doyle.

Many improvements and bugfixes were contributed by the open source community.

json_matchers is Copyright © 2018 thoughtbot.

It is free software, and may be redistributed under the terms specified in the LICENSE file.

json_matchers is maintained and funded by thoughtbot, inc. The names and logos for thoughtbot are trademarks of thoughtbot, inc.

We love open source software! See our other projects. We are available for hire.