Add support for .exactly to the have_relationships(...) matcher

Author: lukemelia

README.md

@@ -37,6 +37,7 @@ Available matchers:
 * `expect(document['data']).to have_jsonapi_attributes(:name, :email, :country).exactly`
 * `expect(document['data']).to have_attribute(:name).with_value('Lucas')`
 * `expect(document['data']).to have_relationships(:posts, :comments)`
+* `expect(document['data']).to have_relationships(:posts, :comments, :likes).exactly`
 * `expect(document['data']).to have_relationship(:posts).with_data([{ 'id' => '1', 'type' => 'posts' }])`
 * `expect(document['data']['relationships']['posts']).to have_links(:self, :related)`
 * `expect(document['data']).to have_link(:self).with_value('http://api.example.com/users/12')`

lib/jsonapi/rspec/relationships.rb

@@ -29,7 +29,14 @@ module Relationships
           actual = JSONAPI::RSpec.as_indifferent_hash(actual)
           return false unless actual.key?('relationships')
 
-          rels.map(&:to_s).all? { |rel| actual['relationships'].key?(rel) }
+          counted = (rels.size == actual['relationships'].keys.size) if @exactly
+
+          rels.map(&:to_s).all? { |rel| actual['relationships'].key?(rel) } \
+            && (counted == @exactly)
+        end
+
+        chain :exactly do
+          @exactly = true
         end
       end
     end

spec/jsonapi/relationships_spec.rb

@@ -23,6 +23,9 @@
   it { expect(doc).not_to have_relationship('authors') }
   it { expect(doc).to have_relationship('user') }
 
+  it { expect(doc).to have_relationships('user', 'comments').exactly }
+  it { expect(doc).not_to have_relationships('comments').exactly }
+
   it do
     expect(doc).to have_relationship('user').with_data(
       { 'id' => '1', 'type' => 'user' }