An example on how to test a static function call in SilverStripe using the Injection system, see discussion at https://groups.google.com/forum/#!topic/silverstripe-dev/f9agsTc3iJo

MockStaticTest.php

<?php

class MockStaticTest extends FunctionalTest {
 
	function foo() {
		// Since Director doesnt extends Object, you have to do it like this, otherwise
		// Director::create() should return an Injected Director
		$director = Injector::inst()->get('Director');
		$director::forceSSL(array('/^Security/', '/^api/'));
	}
 
	function testRedirectsSSL() {
		$stubDirector = $this->getMock('Director', array('forceSSL'));
		Injector::inst()->registerNamedService('Director', new $stubDirector);
		// Ensure that forceSSL was called once with an array as arguments
		$stubDirector::staticExpects($this->once())
			->method('forceSSL')
			->with($this->equalTo(array('/^Security/')));
		// Exercise the method
		$this->foo();
	}
}