Merge pull request #6 from marcgreenstock/master

added interface matcher

README.md

@@ -12,6 +12,7 @@ gem 'rspec-graphql_matchers'
 
 The matchers currently supported are:
    - `expect(a_graphql_object).to have_a_field(field_name).that_returns(valid_type)`
+   - `expect(a_graphql_object).to interface(interface_name, ...)`
    - `expect(a_mutation_type).to have_a_return_field(field_name).returning(valid_type)`
    - `expect(a_mutation_type).to have_an_input_field(field_name).of_type(valid_type)`
    - `expect(a_field).to be_of_type(valid_type)`
@@ -33,6 +34,8 @@ PostType = GraphQL::ObjectType.define do
   name "Post"
   description "A blog post"
 
+  interfaces [GraphQL::Relay::Node.interface]
+
   field :id, !types.ID
 
   field :comments, !types[types.String]
@@ -127,6 +130,20 @@ describe PostType do
 end
 ```
 
+### 4) Test an object's interface implementations:
+
+```ruby
+describe PostType do
+  it 'interfaces Node' do
+    expect(subject).to implement('Node')
+  end
+
+  # Accepts arguments as an array and type objects directly
+  it { is_expected.to implement(GraphQL::Relay::Node.interface) }
+  it { is_expected.not_to implement('OtherInterface') }
+end
+```
+
 The spec will only pass if all attributes/types specified in the hash are
 defined on the field.
 
@@ -151,6 +168,5 @@ contributors are expected to adhere to the
 
 ## License
 
-The gem is available as open source under the terms of the 
+The gem is available as open source under the terms of the
 [MIT License](http://opensource.org/licenses/MIT).
-

lib/rspec/graphql_matchers/implement.rb

@@ -0,0 +1,46 @@
+require_relative 'base_matcher'
+
+module RSpec
+  module GraphqlMatchers
+    class Implement < BaseMatcher
+      def initialize(interface_names)
+        @expected = interface_names.map(&:to_s)
+      end
+
+      def matches?(graph_object)
+        @graph_object = graph_object
+        @actual = actual
+        @expected.each do |name|
+          return false unless @actual.include?(name)
+        end
+      end
+
+      def failure_message
+        message  = "expected interfaces: #{@expected.join(', ')}\n"
+        message += "actual interfaces:   #{@actual.join(', ')}"
+        message
+      end
+
+      def failure_message_when_negated
+        message  = "unexpected interfaces: #{@expected.join(', ')}\n"
+        message += "actual interfaces:     #{@actual.join(', ')}"
+        message
+      end
+
+      def description
+        "implement #{@expected.join(', ')}"
+      end
+
+      private
+
+      def actual
+        if @graph_object.respond_to?(:interfaces)
+          @graph_object.interfaces.map(&:to_s)
+        else
+          raise "Invalid object #{@graph_object} provided to #{matcher_name} " \
+            'matcher. It does not seem to be a valid GraphQL object type.'
+        end
+      end
+    end
+  end
+end

lib/rspec/graphql_matchers/matchers.rb

@@ -2,6 +2,7 @@
 require 'rspec/graphql_matchers/be_of_type'
 require 'rspec/graphql_matchers/accept_arguments'
 require 'rspec/graphql_matchers/have_a_field'
+require 'rspec/graphql_matchers/implement'
 
 module RSpec
   module Matchers
@@ -31,5 +32,9 @@ def have_a_return_field(field_name)
       RSpec::GraphqlMatchers::HaveAField.new(field_name, :return_fields)
     end
     alias have_return_field have_a_return_field
+
+    def implement(*interface_names)
+      RSpec::GraphqlMatchers::Implement.new(interface_names.flatten)
+    end
   end
 end

spec/rspec/implement_matcher_spec.rb

@@ -0,0 +1,65 @@
+require 'spec_helper'
+
+module RSpec::GraphqlMatchers
+  describe 'expect(a_type).to implement(interface_names)' do
+    AnInterface = GraphQL::InterfaceType.define do
+      name 'AnInterface'
+    end
+
+    AnotherInterface = GraphQL::InterfaceType.define do
+      name 'AnotherInterface'
+    end
+
+    subject(:a_type) do
+      GraphQL::ObjectType.define do
+        name 'TestObject'
+        interfaces [
+          GraphQL::Relay::Node.interface,
+          AnInterface
+        ]
+      end
+    end
+
+    it { is_expected.to implement('Node') }
+    it { is_expected.to implement('AnInterface') }
+    it { is_expected.to implement('Node', 'AnInterface') }
+    it { is_expected.to implement(['Node']) }
+    it { is_expected.to implement(['AnInterface']) }
+    it { is_expected.to implement(['Node', 'AnInterface']) }
+    it { is_expected.to implement(GraphQL::Relay::Node.interface, AnInterface) }
+    it { is_expected.to implement([GraphQL::Relay::Node.interface, AnInterface]) }
+
+    it { is_expected.not_to implement('AnotherInterface') }
+    it { is_expected.not_to implement(['AnotherInterface']) }
+    it { is_expected.not_to implement(AnotherInterface) }
+    it { is_expected.not_to implement([AnotherInterface]) }
+
+    it 'fails with a failure message when the type does include the interfaces' do
+      expect { expect(a_type).to implement('AnotherInterface') }
+        .to fail_with(
+          "expected interfaces: AnotherInterface\n" \
+          'actual interfaces:   Node, AnInterface'
+        )
+    end
+
+    it 'provides a description' do
+      matcher = implement('Node, AnInterface')
+      matcher.matches?(a_type)
+
+      expect(matcher.description).to eq('implement Node, AnInterface')
+    end
+
+    context 'when an invalid type is passed' do
+      let(:a_type) { double(to_s: 'InvalidObject') }
+
+      it 'fails with a Runtime error' do
+        expect { expect(a_type).to have_a_field(:id) }
+          .to raise_error(
+            RuntimeError,
+            'Invalid object InvalidObject provided to have_a_field matcher. ' \
+            'It does not seem to be a valid GraphQL object type.'
+          )
+      end
+    end
+  end
+end