test.php

<?php
namespace {
  class A {
		private $sep;

		public function __construct($sep = null) {
			$this->sep = $sep ?: '--';
		}

		public function concat($a, $b) {
			return $a . $this->sep . $b;
		}
	}
}

namespace tests\units {
	use atoum;

	class A extends atoum {
		public function testConcat() {
			$this
				->if($object = new \mock\A())
				->then
					->string($object->concat('foo', 'bar'))->isEqualTo('foo--bar')
			;
		}
	}
}

vendor/bin/atoum -f test.php

> PHP path: /usr/bin/php
> PHP version:
=> PHP 5.4.17 (cli) (built: Aug 18 2013 02:00:51)
=> Copyright (c) 1997-2013 The PHP Group
=> Zend Engine v2.4.0, Copyright (c) 1998-2013 Zend Technologies
> tests\units\A...
[S___________________________________________________________][1/1]
=> Test duration: 0.00 second.
=> Memory usage: 0.25 Mb.
> Total test duration: 0.00 second.
> Total test memory usage: 0.25 Mb.
> Running duration: unknown.
Success (1 test, 1/1 method, 0 void method, 0 skipped method, 2 assertions)!