Proper tests. (#1)

* Add tests for Deserializable::Resource.

* Add codecov integration.

* Add tests for Deserializable::Relationship + fix bad arity.

spec/resource/DSL/has_many_spec.rb

@@ -0,0 +1,118 @@
+require 'spec_helper'
+
+describe JSONAPI::Deserializable::Resource, '.has_many' do
+  let(:deserializable_foo) do
+    Class.new(JSONAPI::Deserializable::Resource) do
+      has_many :foo do |rel, ids, types|
+        field foo_ids: ids
+        field foo_types: types
+        field foo_rel: rel
+      end
+    end
+  end
+
+  context 'relationship is not empty' do
+    let(:payload) do
+      {
+        'data' => {
+          'type' => 'foo',
+          'relationships' => {
+            'foo' => {
+              'data' => [
+                { 'type' => 'foo', 'id' => 'bar' },
+                { 'type' => 'foo', 'id' => 'baz' }
+              ]
+            }
+          }
+        }
+      }
+    end
+
+    it 'creates corresponding fields' do
+      actual = deserializable_foo.call(payload)
+      expected = { foo_ids: %w(bar baz), foo_types: %w(foo foo),
+                   foo_rel: payload['data']['relationships']['foo'] }
+
+      expect(actual).to eq(expected)
+    end
+
+    it 'defaults to creating a field of the same name' do
+      klass = Class.new(JSONAPI::Deserializable::Resource) do
+        has_many :foo
+      end
+      actual = klass.call(payload)
+      expected = { foo: payload['data']['relationships']['foo'] }
+
+      expect(actual).to eq(expected)
+    end
+  end
+
+  context 'relationship is empty' do
+    it 'creates corresponding fields' do
+      payload = {
+        'data' => {
+          'type' => 'foo',
+          'relationships' => {
+            'foo' => {
+              'data' => []
+            }
+          }
+        }
+      }
+      actual = deserializable_foo.call(payload)
+      expected = { foo_ids: [], foo_types: [],
+                   foo_rel: payload['data']['relationships']['foo'] }
+
+      expect(actual).to eq(expected)
+    end
+  end
+
+  context 'relationship is absent' do
+    it 'does not create corresponding fields' do
+      payload = {
+        'data' => {
+          'type' => 'foo',
+          'relationships' => {}
+        }
+      }
+      actual = deserializable_foo.call(payload)
+      expected = {}
+
+      expect(actual).to eq(expected)
+    end
+  end
+
+  context 'there is no relationships member' do
+    it 'does not create corresponding fields' do
+      payload = {
+        'data' => {
+          'type' => 'foo'
+        }
+      }
+      actual = deserializable_foo.call(payload)
+      expected = {}
+
+      expect(actual).to eq(expected)
+    end
+  end
+
+  context 'relationship is not to-many' do
+    it 'does not create corresponding fields' do
+      payload = {
+        'data' => {
+          'type' => 'foo',
+          'relationships' => {
+            'foo' => {
+              'data' => { 'type' => 'foo', 'id' => 'bar' }
+            }
+          }
+        }
+      }
+
+      actual = deserializable_foo.call(payload)
+      expected = {}
+
+      expect(actual).to eq(expected)
+    end
+  end
+end