Add tests.

tests/Unit/Examples/From/ClassTest.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Tests\Unit\Examples\From;
+
+use PHPUnit\Framework\Attributes\Test;
+use Tests\TestCase;
+
+class ClassTest extends TestCase
+{
+    #[Test] public function from(): void
+    {
+        $User = User::from([
+            'firstName' => '1',
+        ]);
+
+        $this->assertEquals('1', $User->first_name);
+    }
+}

tests/Unit/Examples/From/User.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace Tests\Unit\Examples\From;
+
+use Zerotoprod\DataModel\Describe;
+
+class User
+{
+    use \Zerotoprod\DataModel\DataModel;
+
+    public const first_name = 'first_name';
+
+    #[Describe(['from' => 'firstName'])]
+    public string $first_name;
+}