diff --git a/tests/Encoder/Transformers/ModelRelationshipTransformerTest.php b/tests/Encoder/Transformers/ModelRelationshipTransformerTest.php
new file mode 100644
index 0000000..95261eb
--- /dev/null
+++ b/tests/Encoder/Transformers/ModelRelationshipTransformerTest.php
@@ -0,0 +1,175 @@
+<?php
+namespace Czim\JsonApi\Test\Encoder\Transformers;
+
+use Czim\JsonApi\Contracts\Encoder\EncoderInterface;
+use Czim\JsonApi\Contracts\Resource\EloquentResourceInterface;
+use Czim\JsonApi\Encoder\Transformers\ModelRelationshipTransformer;
+use Czim\JsonApi\Support\Resource\RelationshipTransformData;
+use Czim\JsonApi\Test\TestCase;
+use Mockery;
+
+/**
+ * Class ModelRelationshipTransformerTest
+ *
+ * The happy path with sideloaded relation data is tested by integration tests.
+ *
+ * @group encoding
+ */
+class ModelRelationshipTransformerTest extends TestCase
+{
+
+    /**
+     * @test
+     */
+    function it_transforms_relation_data_for_a_model_resource_without_references()
+    {
+        /** @var Mockery\Mock|EloquentResourceInterface $resource */
+        $resource = Mockery::mock(EloquentResourceInterface::class);
+        $resource->shouldReceive('availableIncludes')->andReturn(['test']);
+        $resource->shouldReceive('url')->andReturn('http://test.url');
+        $resource->shouldReceive('id')->andReturn('1');
+        $resource->shouldReceive('type')->andReturn('tests');
+
+        $data = new RelationshipTransformData([
+            'resource'   => $resource,
+            'include'    => 'test',
+            'references' => false,
+            'sideload'   => false,
+        ]);
+
+        $transformer = new ModelRelationshipTransformer;
+        $transformer->setEncoder($this->getMockEncoder());
+
+        static::assertEquals(
+            [
+                'links' => [
+                    'self'    => 'http://test.url/1/relationships/test',
+                    'related' => 'http://test.url/1/related/test',
+                ]
+            ],
+            $transformer->transform($data)
+        );
+    }
+
+    /**
+     * @test
+     */
+    function it_transforms_relation_data_for_a_model_resource_without_links_if_configured()
+    {
+        /** @var Mockery\Mock|EloquentResourceInterface $resource */
+        $resource = Mockery::mock(EloquentResourceInterface::class);
+        $resource->shouldReceive('availableIncludes')->andReturn(['test']);
+
+        $this->app['config']->set('jsonapi.transform.links.relationships', false);
+        $this->app['config']->set('jsonapi.transform.links.related', false);
+
+        $data = new RelationshipTransformData([
+            'resource'   => $resource,
+            'include'    => 'test',
+            'references' => false,
+            'sideload'   => false,
+        ]);
+
+        $transformer = new ModelRelationshipTransformer;
+        $transformer->setEncoder($this->getMockEncoder());
+
+        static::assertEquals([], $transformer->transform($data));
+    }
+
+    /**
+     * @test
+     */
+    function it_transforms_relation_data_for_a_model_resource_with_references()
+    {
+        /** @var Mockery\Mock|EloquentResourceInterface $resource */
+        $resource = Mockery::mock(EloquentResourceInterface::class);
+        $resource->shouldReceive('availableIncludes')->andReturn(['test']);
+        $resource->shouldReceive('url')->andReturn('http://test.url');
+        $resource->shouldReceive('id')->andReturn('1');
+        $resource->shouldReceive('type')->andReturn('tests');
+        $resource->shouldReceive('relationshipReferences')->andReturn(['type' => 'tests', 'id' => '2']);
+
+        $data = new RelationshipTransformData([
+            'resource'   => $resource,
+            'include'    => 'test',
+            'references' => true,
+            'sideload'   => false,
+        ]);
+
+        $transformer = new ModelRelationshipTransformer;
+        $transformer->setEncoder($this->getMockEncoder());
+
+        static::assertEquals(
+            [
+                'links' => [
+                    'self'    => 'http://test.url/1/relationships/test',
+                    'related' => 'http://test.url/1/related/test',
+                ],
+                'data' => [
+                    'type' => 'tests',
+                    'id'   => '2',
+                ],
+            ],
+            $transformer->transform($data)
+        );
+    }
+
+    /**
+     * @test
+     * @expectedException \Czim\JsonApi\Exceptions\EncodingException
+     */
+    function it_throws_an_exception_if_data_does_not_indicate_a_valid_include()
+    {
+        /** @var Mockery\Mock|EloquentResourceInterface $resource */
+        $resource = Mockery::mock(EloquentResourceInterface::class);
+        $resource->shouldReceive('availableIncludes')->andReturn([]);
+        $resource->shouldReceive('url')->andReturn('http://test.url');
+        $resource->shouldReceive('id')->andReturn('1');
+        $resource->shouldReceive('type')->andReturn('tests');
+
+        $data = new RelationshipTransformData([
+            'resource'   => $resource,
+            'include'    => 'test',
+            'references' => false,
+            'sideload'   => true,
+        ]);
+
+        $transformer = new ModelRelationshipTransformer;
+        $transformer->setEncoder($this->getMockEncoder());
+
+        $transformer->transform($data);
+    }
+
+    /**
+     * @test
+     * @expectedException \InvalidArgumentException
+     */
+    function it_throws_an_exception_if_data_is_not_a_relationship_data_instance()
+    {
+        $transformer = new ModelRelationshipTransformer;
+        $transformer->setEncoder($this->getMockEncoder());
+
+        $transformer->transform($this);
+    }
+
+    /**
+     * @test
+     * @expectedException \Czim\JsonApi\Exceptions\EncodingException
+     */
+    function it_throws_an_exception_if_no_resource_is_set_in_data()
+    {
+        $transformer = new ModelRelationshipTransformer;
+        $transformer->setEncoder($this->getMockEncoder());
+
+        $transformer->transform(new RelationshipTransformData([]));
+    }
+
+    /**
+     * @return EncoderInterface|Mockery\MockInterface
+     */
+    protected function getMockEncoder()
+    {
+        return Mockery::mock(EncoderInterface::class);
+    }
+
+}