diff --git a/tests/MainEntity.php b/tests/MainEntity.php
new file mode 100644
index 0000000..90299d0
--- /dev/null
+++ b/tests/MainEntity.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Graphpommando\Tests;
+
+final class MainEntity implements \Graphpommando\Entity
+{
+    public int $fieldInt;
+    public float $fieldFloat;
+    public bool $fieldBool;
+    public string $fieldString;
+    #[\Graphpommando\Attribute\Alias('fieldString')]
+    public string $fieldAliasedString;
+    public SubEntity $subfield;
+    #[\Graphpommando\Attribute\OfType('string', false)]
+    public array $listOfStrings;
+    #[\Graphpommando\Attribute\OfType('array', false, ['string', false])]
+    public array $matrixOfStrings;
+    #[\Graphpommando\Attribute\OfType(SubEntity::class, false)]
+    public array $listOfSubfields;
+    #[\Graphpommando\Attribute\OfType('array', false, [SubEntity::class, false])]
+    public array $matrixOfSubfields;
+    #[\Graphpommando\Attribute\Argument('arg1', \Graphpommando\Value\VariableValue::class, ['var1'])]
+    public int $fieldWithArgs;
+    #[\Graphpommando\Attribute\ConstructorPass]
+    public \DateTime $fieldDateTime;
+    public ?int $fieldNullable;
+}
diff --git a/tests/SubEntity.php b/tests/SubEntity.php
new file mode 100644
index 0000000..bb1023f
--- /dev/null
+++ b/tests/SubEntity.php
@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Graphpommando\Tests;
+
+final class SubEntity implements \Graphpommando\Entity
+{
+    public int $fieldInt;
+}
diff --git a/tests/Unit/EntityHydratorTest.php b/tests/Unit/EntityHydratorTest.php
new file mode 100644
index 0000000..262ed01
--- /dev/null
+++ b/tests/Unit/EntityHydratorTest.php
@@ -0,0 +1,75 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Graphpommando\Tests\Unit;
+
+final class EntityHydratorTest extends \PHPUnit\Framework\TestCase
+{
+    public function testSimple() : void
+    {
+        $hydrator = new \Graphpommando\EntityHydrator();
+        $result = $hydrator->hydrate(\Graphpommando\Tests\MainEntity::class, \Infinityloop\Utils\Json::fromNative((object) [
+            'data' => [
+                'fieldInt' => 1,
+                'fieldFloat' => 2.0,
+                'fieldBool' => true,
+                'fieldString' => '3',
+                'fieldAliasedString' => '4',
+                'subfield' => ['fieldInt' => 5],
+                'listOfStrings' => ['6', '7'],
+                'matrixOfStrings' => [['8'], [], ['9', '10']],
+                'listOfSubfields' => [['fieldInt' => 11], ['fieldInt' => 12]],
+                'matrixOfSubfields' => [[['fieldInt' => 13], ['fieldInt' => 14]], [['fieldInt' => 15]]],
+                'fieldWithArgs' => 16,
+                'fieldDateTime' => '2021-01-01',
+                'fieldNullable' => null,
+            ],
+        ])->toString());
+
+        self::assertInstanceOf(\Graphpommando\Tests\MainEntity::class, $result);
+        \assert($result instanceof \Graphpommando\Tests\MainEntity);
+        self::assertSame(1, $result->fieldInt);
+        self::assertSame(2.0, $result->fieldFloat);
+        self::assertTrue($result->fieldBool);
+        self::assertSame('3', $result->fieldString);
+        self::assertSame('4', $result->fieldAliasedString);
+        self::assertInstanceOf(\Graphpommando\Tests\SubEntity::class, $result->subfield);
+        self::assertSame(5, $result->subfield->fieldInt);
+        self::assertSame(16, $result->fieldWithArgs);
+        self::assertInstanceOf(\DateTime::class, $result->fieldDateTime);
+        self::assertSame($result->fieldDateTime->format('Y-m-d'), '2021-01-01');
+        self::assertNull($result->fieldNullable);
+        self::assertIsArray($result->listOfStrings);
+
+        foreach ($result->listOfStrings as $field) {
+            self::assertIsString($field);
+        }
+
+        self::assertIsArray($result->listOfSubfields);
+
+        foreach ($result->listOfSubfields as $field) {
+            self::assertInstanceOf(\Graphpommando\Tests\SubEntity::class, $field);
+        }
+
+        self::assertIsArray($result->matrixOfStrings);
+
+        foreach ($result->matrixOfStrings as $field) {
+            self::assertIsArray($field);
+
+            foreach ($field as $subField) {
+                self::assertIsString($subField);
+            }
+        }
+
+        self::assertIsArray($result->matrixOfSubfields);
+
+        foreach ($result->matrixOfSubfields as $field) {
+            self::assertIsArray($field);
+
+            foreach ($field as $subField) {
+                self::assertInstanceOf(\Graphpommando\Tests\SubEntity::class, $subField);
+            }
+        }
+    }
+}
diff --git a/tests/Unit/QueryBuilderTest.php b/tests/Unit/QueryBuilderTest.php
new file mode 100644
index 0000000..2461774
--- /dev/null
+++ b/tests/Unit/QueryBuilderTest.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Graphpommando\Tests\Unit;
+
+final class QueryBuilderTest extends \PHPUnit\Framework\TestCase
+{
+    public function testSimple() : void
+    {
+        $builder = new \Graphpommando\QueryBuilder();
+        $operation = new \Graphpommando\DefaultOperation('query', [], [], \Graphpommando\Tests\MainEntity::class);
+
+        self::assertSame(
+            'query{fieldInt fieldFloat fieldBool fieldString fieldAliasedString: fieldString subfield{fieldInt} listOfStrings matrixOfStrings listOfSubfields{fieldInt} matrixOfSubfields{fieldInt} fieldWithArgs(arg1: $var1) fieldDateTime fieldNullable}',
+            $builder->build($operation),
+        );
+    }
+}