diff --git a/tests/functions/get_formatted_filesize_test.php b/tests/functions/get_formatted_filesize_test.php
new file mode 100644
index 0000000000..1cc7ddf9ec
--- /dev/null
+++ b/tests/functions/get_formatted_filesize_test.php
@@ -0,0 +1,50 @@
+<?php
+/**
+*
+* @package testing
+* @copyright (c) 2012 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+require_once dirname(__FILE__) . '/../../phpBB/includes/functions.php';
+
+class phpbb_get_formatted_filesize_test extends phpbb_test_case
+{
+	public function get_formatted_filesize_test_data()
+	{
+		return array(
+			// exact powers of 2
+			array(1, '1 BYTES'),
+			array(1024, '1 KIB'),
+			array(1048576, '1 MIB'),
+			array(1073741824, '1 GIB'),
+			array(1099511627776, '1 TIB'),
+
+			array(0, '0 BYTES'),
+			array(2, '2 BYTES'),
+			array(-2, '-2 BYTES'),
+
+			array(1023, '1023 BYTES'),
+			array(1025, '1 KIB'),
+			array(-1023, '-1023 BYTES'),
+			array(-1025, '-1025 BYTES'),
+
+			array(1048575, '1024 KIB'),
+
+			// large negatives
+			array(-1073741824, '-1073741824 BYTES'),
+			array(-1099511627776, '-1099511627776 BYTES'),
+		);
+	}
+
+	/**
+	* @dataProvider get_formatted_filesize_test_data
+	*/
+	public function test_get_formatted_filesize($input, $expected)
+	{
+		$output = get_formatted_filesize($input);
+
+		$this->assertEquals($expected, $output);
+	}
+}