DEV: Add schema checking to api doc testing (#11721)

* DEV: Add schema checking to api doc testing

This commit improves upon rswag which lacks schema checking. rswag
really only checks that the https status matches, but this change adds
in the json-schema_builder gem which also has schema validation.

Now we can define schemas for each of our requests/responses in the
`spec/requests/api/schemas` directory which will make our documentation
specs a lot cleaner.

If we update a serializer by either adding or removing an attribute the
tests will now fail (this is a good thing!). Also if you change the type
of an attribute say from an array to a string the tests will now fail.
This will help significantly with keeping the docs in sync with actual
code changes! Now if you change how an endpoint will respond you will
have to update the docs too in order for the tests to pass. :D

This PR is inspired by:

 https://www.tealhq.com/post/how-teal-keeps-their-api-tests-and-documentation-in-sync

* Swap out json schema validator gem

Swapped out the outdated json-schema_builder gem with the json_schemer
gem.

* Add validation fields to schema

In order to have "strict" validation we need to add
`additionalProperties: false` to the schema, and we need to specify
which attributes are required.

Updated the debugging test output to print out the error details if
there are any.

Gemfile

@@ -167,6 +167,7 @@ group :test, :development do
   gem 'parallel_tests'
 
   gem 'rswag-specs'
+  gem 'json_schemer'
 end
 
 group :development do

Gemfile.lock

@@ -114,6 +114,8 @@ GEM
       in_threads (~> 1.3)
       progress (~> 3.0, >= 3.0.1)
     docile (1.3.5)
+    ecma-re-validator (0.3.0)
+      regexp_parser (~> 2.0)
     email_reply_trimmer (0.1.13)
     ember-data-source (3.0.2)
       ember-source (>= 2, < 3.0)
@@ -141,6 +143,7 @@ GEM
     globalid (0.4.2)
       activesupport (>= 4.2.0)
     guess_html_encoding (0.0.11)
+    hana (1.3.7)
     hashdiff (1.0.1)
     hashie (4.1.0)
     highline (2.0.3)
@@ -159,6 +162,11 @@ GEM
     json (2.5.1)
     json-schema (2.8.1)
       addressable (>= 2.4)
+    json_schemer (0.2.17)
+      ecma-re-validator (~> 0.3)
+      hana (~> 1.3)
+      regexp_parser (~> 2.0)
+      uri_template (~> 0.7)
     jwt (2.2.2)
     kgio (2.11.3)
     libv8 (8.4.255.0)
@@ -432,6 +440,7 @@ GEM
       kgio (~> 2.6)
       raindrops (~> 0.7)
     uniform_notifier (1.13.2)
+    uri_template (0.7.0)
     webmock (3.11.1)
       addressable (>= 2.3.6)
       crack (>= 0.3.2)
@@ -494,6 +503,7 @@ DEPENDENCIES
   htmlentities
   http_accept_language
   json
+  json_schemer
   listen
   lograge
   logstash-event

spec/requests/api/schemas/tag_group_schemas.rb

@@ -0,0 +1,77 @@
+# frozen_string_literal: true
+
+module SpecSchemas
+
+  class TagGroupCreateRequest
+    def schemer
+      schema = {
+        'type' => 'object',
+        'additionalProperties' => false,
+        'properties' => {
+          'name' => {
+            'type' => 'string',
+          }
+        },
+        'required' => ['name']
+      }
+    end
+  end
+
+  class TagGroupResponse
+    def schemer
+      schema = {
+        'type' => 'object',
+        'additionalProperties' => false,
+        'properties' => {
+          'tag_group' => {
+            'type' => 'object',
+            'properties' => {
+              'id' => {
+                'type' => 'integer',
+              },
+              'name' => {
+                'type' => 'string',
+              },
+              'tag_names' => {
+                'type' => 'array',
+                'items' => {
+                  'type' => 'string'
+                }
+              },
+              'parent_tag_name' => {
+                'type' => 'array',
+                'items' => {
+                  'type' => 'string'
+                }
+              },
+              'one_per_topic' => {
+                'type' => 'boolean',
+              },
+              'permissions' => {
+                'type' => 'object',
+                'properties' => {
+                  'everyone' => {
+                    'type' => 'integer',
+                    'example' => 1
+                  }
+                }
+              }
+            },
+            'required' => [
+              'id',
+              'name',
+              'tag_names',
+              'parent_tag_name',
+              'one_per_topic',
+              'permissions'
+            ]
+          }
+        },
+        'required' => [
+          'tag_group'
+        ]
+      }
+    end
+  end
+
+end

spec/requests/api/shared/shared_examples.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+RSpec.shared_examples "a JSON endpoint" do |expected_response_status|
+  before do |example|
+    submit_request(example.metadata)
+  end
+
+  describe "response status" do
+    it "returns expected response status" do
+      expect(response.status).to eq(expected_response_status)
+    end
+  end
+
+  describe "request body" do
+    it "matches the documented request schema" do |example|
+      schemer = JSONSchemer.schema(expected_request_schema.schemer)
+      valid = schemer.valid?(params)
+      unless valid # for debugging
+        puts params
+        puts schemer.validate(params).to_a[0]["details"]
+      end
+      expect(valid).to eq(true)
+    end
+  end
+
+  describe "response body" do
+    let(:json_response) { JSON.parse(response.body) }
+
+    it "matches the documented response schema" do  |example|
+      schemer = JSONSchemer.schema(
+        expected_response_schema.schemer,
+      )
+      valid = schemer.valid?(json_response)
+      unless valid # for debugging
+        puts json_response
+        puts schemer.validate(json_response).to_a[0]["details"]
+      end
+      expect(valid).to eq(true)
+    end
+  end
+end

spec/requests/api/tags_spec.rb

@@ -60,46 +60,22 @@ describe 'tags' do
     post 'Creates a tag group' do
       tags 'Tags'
       consumes 'application/json'
-      parameter name: :post_body, in: :body, schema: {
+      expected_request_schema = SpecSchemas::TagGroupCreateRequest.new
-        type: :object,
+
-        properties: {
+      parameter name: :params, in: :body, schema: expected_request_schema.schemer
-          name: { type: :string }
-        },
-        required: [ 'name' ]
-      }
 
       produces 'application/json'
       response '200', 'tag group created' do
-        schema type: :object, properties: {
+        expected_response_schema = SpecSchemas::TagGroupResponse.new
-          tag_group: {
-            type: :object,
-            properties: {
-              id: { type: :integer },
-              name: { type: :string },
-              tag_names: {
-                type: :array,
-                items: {
-                },
-              },
-              parent_tag_name: {
-                type: :array,
-                items: {
-                },
-              },
-              one_per_topic: { type: :boolean },
-              permissions: {
-                type: :object,
-                properties: {
-                  everyone: { type: :integer },
-                }
-              },
-            }
-          },
-        }
 
-        let(:post_body) { { name: 'todo' } }
+        let(:params) { { 'name' => 'todo' } }
 
-        run_test!
+        schema(expected_response_schema.schemer)
+
+        it_behaves_like "a JSON endpoint", 200 do
+          let(:expected_response_schema) { expected_response_schema }
+          let(:expected_request_schema) { expected_request_schema }
+        end
       end
     end
 

spec/swagger_helper.rb

@@ -1,6 +1,13 @@
 # frozen_string_literal: true
 
 require 'rails_helper'
+require 'json_schemer'
+
+# Require schema files
+Dir["./spec/requests/api/schemas/*.rb"].each { |file| require file }
+
+# Require shared spec examples
+Dir["./spec/requests/api/shared/*.rb"].each { |file| require file }
 
 RSpec.configure do |config|
   # Specify a root folder where Swagger JSON files are generated