This is an example of autoloading classes and including unit tests.

autoload.php

@@ -0,0 +1,41 @@
+<?php
+spl_autoload_register(function ($class) {
+
+	// the package namespace
+	$ns = 'Friendica\Directory';
+
+	// what prefixes should be recognized?
+	$prefixes = array(
+		"{$ns}\\" => array(
+			__DIR__ . '/src',
+			__DIR__ . '/tests/unit/src',
+		),
+	);
+
+	// go through the prefixes
+	foreach ($prefixes as $prefix => $dirs) {
+
+		// does the requested class match the namespace prefix?
+		$prefix_len = strlen($prefix);
+		if (substr($class, 0, $prefix_len) !== $prefix) {
+			continue;
+		}
+
+		// strip the prefix off the class
+		$class = substr($class, $prefix_len);
+
+		// a partial filename
+		$part = str_replace('\\', DIRECTORY_SEPARATOR, $class) . '.php';
+
+		// go through the directories to find classes
+		foreach ($dirs as $dir) {
+			$dir = str_replace('/', DIRECTORY_SEPARATOR, $dir);
+			$file = $dir . DIRECTORY_SEPARATOR . $part;
+			if (is_readable($file)) {
+				require $file;
+				return;
+			}
+		}
+	}
+
+});