diff --git a/src/ApiModel.php b/src/ApiModel.php
index cff1668..64d566c 100644
--- a/src/ApiModel.php
+++ b/src/ApiModel.php
@@ -183,7 +183,7 @@ public function __set($key, $value)
         }
     }
 
-    protected function hasRelationship($key):  ? string
+    protected function hasRelationship($key): ?string
     {
         if (method_exists($this, $key)
             && ($this->{$key}() instanceof Relationship || $this->{$key}() instanceof SingleRelationship)) {
@@ -226,7 +226,7 @@ public function __get($key)
      *
      * @return bool
      */
-    public function exists() : bool
+    public function exists(): bool
     {
         foreach ($this->requiredParameters as $parameter) {
             if (!$this->has($parameter)) {
diff --git a/src/Relationships/SingleRelationship.php b/src/Relationships/SingleRelationship.php
index 9078943..9016452 100644
--- a/src/Relationships/SingleRelationship.php
+++ b/src/Relationships/SingleRelationship.php
@@ -15,7 +15,7 @@ public function setRelateClassQualifiedName(string $class)
         return $this;
     }
 
-    public function getRelatedClassQualifiedName():string
+    public function getRelatedClassQualifiedName(): string
     {
         return $this->relatedClassQualifiedName;
     }
diff --git a/tests/Fakes/City.php b/tests/Fakes/City.php
index 8ff113b..0549219 100644
--- a/tests/Fakes/City.php
+++ b/tests/Fakes/City.php
@@ -8,6 +8,6 @@ class City extends ApiModel
 {
     public function partnerCity()
     {
-        return $this->hasOne(City::class, 'partner_city');
+        return $this->hasOne(self::class, 'partner_city');
     }
 }
diff --git a/tests/ModelTest.php b/tests/ModelTest.php
index 354c1cd..8f092b0 100644
--- a/tests/ModelTest.php
+++ b/tests/ModelTest.php
@@ -49,8 +49,7 @@ public function it_should_assign_a_value_to_a_parameter()
     /** @test */
     public function it_should_throw_an_error_on_immutble_parameters()
     {
-        $model = new class() extends ApiModel
-        {
+        $model = new class() extends ApiModel {
             public function getFooAttribute()
             {
                 return 'bar';
@@ -66,8 +65,7 @@ public function getFooAttribute()
     /** @test */
     public function it_should_throw_an_error_on_immutble_methods()
     {
-        $model = new class() extends ApiModel
-        {
+        $model = new class() extends ApiModel {
             public function fakeMethod(): string
             {
                 return 'I return a string';
@@ -83,8 +81,7 @@ public function fakeMethod(): string
     /** @test */
     public function it_should_return_null_getting_value_on_defined_methods()
     {
-        $model = new class() extends ApiModel
-        {
+        $model = new class() extends ApiModel {
             public function fakeMethod(): string
             {
                 return 'I return a string';
@@ -157,7 +154,7 @@ public function it_should_cast_single_relationship_to_model()
         $harbor = new Harbor([
             'city' => [
                 'data' => [
-                    'id' => 1,
+                    'id'   => 1,
                     'name' => 'Montevideo',
                 ],
             ],
@@ -172,7 +169,7 @@ public function it_should_cast_single_relationship_to_model_and_preserve_attribu
         $harbor = new Harbor([
             'city' => [
                 'data' => [
-                    'id' => 1,
+                    'id'   => 1,
                     'name' => 'Montevideo',
                 ],
             ],
@@ -186,7 +183,7 @@ public function it_should_cast_single_relationship_to_model_event_without_data()
     {
         $harbor = new Harbor([
             'city' => [
-                'id' => 1,
+                'id'   => 1,
                 'name' => 'Montevideo',
             ],
         ]);
@@ -199,7 +196,7 @@ public function it_should_refresh_a_relationship_when_setting_new_value()
     {
         $harbor = new Harbor([
             'city' => [
-                'id' => 1,
+                'id'   => 1,
                 'name' => 'Montevideo',
             ],
         ]);
@@ -217,7 +214,7 @@ public function it_should_property_from_relationship_should_be_accessed()
         $harbor = new Harbor([
             'city' => [
                 'data' => [
-                    'id' => 1,
+                    'id'   => 1,
                     'name' => 'Montevideo',
                 ],
             ],
@@ -233,7 +230,7 @@ public function it_should_property_from_relationship_should_be_accessed_as_objec
         $harbor = new Harbor([
             'city' => [
                 'data' => [
-                    'id' => 1,
+                    'id'   => 1,
                     'name' => 'Montevideo',
                 ],
             ],
@@ -249,7 +246,7 @@ public function it_should_property_from_relationship_should_be_accessed_double()
         $harbor = new Harbor([
             'city' => [
                 'data' => [
-                    'id' => 1,
+                    'id'   => 1,
                     'name' => 'Montevideo',
                 ],
             ],
@@ -265,10 +262,10 @@ public function it_should_preserve_attributes_for_child_properties()
         $harbor = new Harbor([
             'city' => [
                 'data' => [
-                    'id' => 1,
-                    'name' => 'Montevideo',
+                    'id'           => 1,
+                    'name'         => 'Montevideo',
                     'partner_city' => [
-                        'id' => 2,
+                        'id'   => 2,
                         'name' => 'Berlin',
                     ],
                 ],
@@ -286,11 +283,11 @@ public function it_should_return_a_collection_of_boats()
             'boats' => [
                 'data' => [
                     [
-                        'id' => 1,
+                        'id'   => 1,
                         'name' => 'Queen Mary',
                     ],
                     [
-                        'id' => 2,
+                        'id'   => 2,
                         'name' => 'Reconcho',
                     ],
                 ],
@@ -307,11 +304,11 @@ public function it_should_refresh_a_collection_of_relationships()
             'boats' => [
                 'data' => [
                     [
-                        'id' => 1,
+                        'id'   => 1,
                         'name' => 'Queen Mary',
                     ],
                     [
-                        'id' => 2,
+                        'id'   => 2,
                         'name' => 'Reconcho',
                     ],
                 ],
@@ -340,9 +337,9 @@ public function it_should_eager_load_default_relationships()
             'visited_cities' => [
                 'data' => [
                     [
-                        'name' => 'Montevideo',
+                        'name'         => 'Montevideo',
                         'partner_city' => [
-                            'id' => 2,
+                            'id'   => 2,
                             'name' => 'Berlin',
                         ],
                     ],
@@ -360,8 +357,7 @@ public function it_should_eager_load_default_relationships()
     /** @test */
     public function it_should_not_eager_load_any_relationship_if_not_in_include_default_array()
     {
-        $model = new class(['visited_cities' => ['data' => [['name' => 'Montevideo'], ['name' => 'London']]]]) extends ApiModel
-        {
+        $model = new class(['visited_cities' => ['data' => [['name' => 'Montevideo'], ['name' => 'London']]]]) extends ApiModel {
             public function visitedCities()
             {
                 return $this->hasMany(City::class, 'visited_cities');