diff --git a/tests/FormatterTest.php b/tests/FormatterTest.php
new file mode 100644
index 0000000..66f0516
--- /dev/null
+++ b/tests/FormatterTest.php
@@ -0,0 +1,48 @@
+<?php
+/**
+ * Wingman
+ *
+ * @link      http://github.com/mleko/wingman
+ * @copyright Copyright (c) 2017 Daniel Król
+ * @license   MIT
+ */
+
+namespace Mleko\Wingman;
+
+use PHPUnit\Framework\TestCase;
+
+class FormatterTest extends TestCase
+{
+    public static function stdClass(array $data)
+    {
+        $stdClass = new \stdClass();
+        foreach ($data as $key => $value) {
+            $stdClass->{$key} = $value;
+        }
+        return $stdClass;
+    }
+
+    /**
+     * @param $input
+     * @param $comparator
+     * @param $expected
+     * @dataProvider sortDataProvider
+     */
+    public function testSort($input, $comparator, $expected)
+    {
+        $actual = Formatter::sort($input, $comparator);
+        $this->assertEquals($expected, $actual);
+        $actualKeyMap = (array_keys((array)$actual));
+        $expectedKeyMap = (array_keys((array)$expected));
+        $this->assertEquals($expectedKeyMap, $actualKeyMap);
+    }
+
+    public function sortDataProvider()
+    {
+        return [
+            [self::stdClass(["b" => 1, "a" => 2, "c" => "c"]), "strcmp", self::stdClass(["a" => 2, "b" => 1, "c" => "c"])],
+            [1, "strcmp", 1],
+            [[1, 3, 2], "strcmp", [1, 3, 2]]
+        ];
+    }
+}