add tests

tests/Unit/UlidGeneratorTest.php

@@ -0,0 +1,33 @@
+<?php declare(strict_types=1);
+
+use Doctrine\ORM\EntityManager;
+use Lubiana\DoctrineUlid\IdGenerator\UlidGenerator;
+use Symfony\Component\Uid\Factory\UlidFactory;
+use Symfony\Component\Uid\Ulid;
+
+test(
+    'UlidGenerator constructs without factory and generate Id',
+    function (): void {
+        $ulidGenerator = new UlidGenerator;
+        $em = createMock(EntityManager::class);
+        $id = $ulidGenerator->generateId($em, null);
+        expect($id)
+            ->toBeInstanceOf(Ulid::class);
+    },
+);
+
+test(
+    'UlidGenerator constructs with factory and generate Id',
+    function (): void {
+        $factory = Mockery::mock(UlidFactory::class);
+        $ulid = new Ulid;
+        $factory->shouldReceive('create')
+            ->andReturn($ulid)
+            ->once();
+        $ulidGenerator = new UlidGenerator($factory);
+        $em = Mockery::mock(EntityManager::class);
+        $id = $ulidGenerator->generateId($em, null);
+        expect($id)
+            ->toBe($ulid);
+    },
+);