diff --git a/tests/Alcaeus/MongoDbAdapter/TypeConverterTest.php b/tests/Alcaeus/MongoDbAdapter/TypeConverterTest.php
new file mode 100644
index 00000000..38fcad7b
--- /dev/null
+++ b/tests/Alcaeus/MongoDbAdapter/TypeConverterTest.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace Alcaeus\MongoDbAdapter\Tests;
+
+use MongoDB\BSON;
+use MongoDB\Driver\Exception;
+use Alcaeus\MongoDbAdapter\TypeConverter;
+use MongoDB\Model\BSONDocument;
+
+class TypeConverterTest extends TestCase
+{
+    /**
+     * @dataProvider converterData
+     */
+    public function testFromLegacy($legacyValue, $modernValue)
+    {
+        $this->skipTestIf(extension_loaded('mongo'));
+        $this->assertEquals($modernValue, TypeConverter::fromLegacy($legacyValue));
+    }
+
+    public static function converterData()
+    {
+        $id = str_repeat('0123', 6);
+
+        return [
+            'objectId' => [
+                new \MongoId($id), new BSON\ObjectID($id)
+            ],
+            'numericArray' => [
+                ['foo', 'bar'], ['foo', 'bar']
+            ],
+            'hashWithNumericKeys' => [
+                (object) ['foo', 'bar'], new BSONDocument(['foo', 'bar'])
+            ],
+            'hash' => [
+                ['foo' => 'bar'], new BSONDocument(['foo' => 'bar'])
+            ],
+            'nestedArrays' => [
+                [['foo' => 'bar']], [new BSONDocument(['foo' => 'bar'])]
+            ],
+        ];
+    }
+}